Author: "Knafo, William" - Searchworks@Jio Institute Digital Library Search Results

Your search keyword '"Knafo, William"' showing total 96 results

Start Over Author "Knafo, William"

96 results on '"Knafo, William"'

1. Magnetism in heavy-f-electron metals

Author: Knafo, William
Subjects: Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity
Abstract: In this document, I present a personal view on the heavy-fermion problem, within a phenomenological approach guided by experiments. This review presents a set of 'historical' works which established the ground bases of the thematic during the last decades. An exhaustive and systematic approach is privileged. After a general presentation in Chapter 2, the properties of heavy-fermion paramagnets, antiferromagnets, and ferromagnets are considered in Chapters 3, 4, and 5, respectively. Chapters 6 and 7 are dedicated to two specific compounds, URu$_2$Si$_2$ for which a 'hidden-order' phase constitutes a more-than-thirty-years-old unsolved mystery, and UTe$_2$, where multiple superconducting phases have been discovered in the last two years. Experiments performed using a panel of techniques ranging from microscopic (neutron scattering, NMR, etc.) to thermodynamic (specific heat, magnetization, etc.) and transport (electrical resistivity, etc.) probes, under extreme conditions of low temperatures, intense magnetic fields and high pressures, are reviewed. They show that magnetism plays a central role in the quantum critical properties of heavy-fermion systems. An emphasis is given to the intersite magnetic fluctuations, presented as the driving force for a heavy Fermi liquid, precursor of quantum magnetic criticality ending in magnetically-ordered phases. They are also suspected to drive an unconventional mechanism for superconductivity, which develops in the vicinity of quantum magnetic phase transitions induced under pressure or magnetic field. The appearance of magnetic fluctuations and ultimately magnetic order in heavy-fermion compounds occurs in a nearly-integer-valence regime, in which $f$ electrons have a dual itinerant-localized character. Fermi-surface and valence studies, which give complementary information about this duality, are also considered., Comment: This document is a review on the quantum magnetic properties of heavy-fermion $f$-electron metals. It is a 'light' version of the manuscript prepared for my 'Habilitation \`{a} diriger des recherches', sent to the Jury on 29 October 2020 and defended on 9 April 2021. Small modifications were made to the manuscript on 20 July 2021. - 7 Chapters, 258 pages, 130 Mo (may be slow to download)
Published: 2021

2. Field-Induced Superconductivity near the Superconducting Critical Pressure in UTe2

Author: Aoki, Dai, Kimata, Motoi, Sato, Yoshiki J., Knebel, Georg, Honda, Fuminori, Nakamura, Ai, Li, Dexin, Homma, Yoshiya, Shimizu, Yusei, Knafo, William, Braithwaite, Daniel, Valiska, Michal, Pourret, Alexandre, Brison, Jean-Pascal, and Flouquet, Jacques
Subjects: Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity
Abstract: We report the magnetoresistance in the novel spin-triplet superconductor UTe2 under pressure close to the critical pressure Pc, where the superconducting phase terminates, for field along the three a, b and c-axes in the orthorhombic structure. The superconducting phase for H // a-axis just below Pc shows a field-reentrant behavior due to the competition with the emergence of magnetic order at low fields. The upper critical field Hc2 for H // c-axis shows a quasi-vertical increase in the H-T phase diagram just below Pc, indicating that superconductivity is reinforced by the strong fluctuations which persist even at high fields above 20T. Increasing pressure leads to the disappearance of superconductivity at zero field with the emergence of magnetic order. Surprisingly, field-induced superconductivity is observed at high fields, where a spin-polarized state is realized due to the suppression of the magnetic ordered phases; the spin-polarized state is favorable for superconductivity, whereas the magnetic ordered phase at low field seems to be unfavorable. The huge Hc2 in the spin-polarized state seems to imply a spin-triplet state. Contrary to the a- and c-axes, no field-reinforcement of superconductivity occurs for magnetic field along the b-axis. We compare the results with the field-reentrant superconductivity above the metamagnetic field, Hm for the field direction tilted by about 30 deg. from b to c-axis at ambient pressure as well as the field-reentrant (-reinforced) superconductivity in ferromagnetic superconductors, URhGe and UCoGe., Comment: 7 pages, 5 figures, submitted to J. Phys. Soc. Jpn
Published: 2021
Full Text: View/download PDF

3. Evidence of Fermi-Surface Reconstruction at the Metamagnetic Transition of the Strongly Correlated Superconductor UTe2

Author: Niu, Qun, Knebel, Georg, Braithwaite, Daniel, Aoki, Dai, Lapertot, Gérard, Vališka, Michal, Seyfarth, Gabriel, Knafo, William, Helm, Toni, Brison, Jean-Pascal, Flouquet, Jacques, and Pourret, Alexandre
Subjects: Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity
Abstract: Thermoelectric power ($S$) and Hall effect ($R_\mathrm{H}$) measurements on the paramagnetic superconductor UTe$_2$ with magnetic field applied along the hard magnetization $b$-axis are reported. The first order nature of the metamagnetic transition at $H_\mathrm{m}=H^b_\mathrm{c2}=35$~T leads to drastic consequences on $S$ and $R_\mathrm{H}$. In contrast to the field dependence of the specific heat in the normal state through $H_\mathrm{m}$, $S(H)$ is not symmetric with respect to $H_\mathrm{m}$. This implies a strong interplay between ferromagnetic (FM) fluctuations and a Fermi-surface reconstruction at $H_\mathrm{m}$. $R_\mathrm{H}$ is very well described by incoherent skew scattering above the coherence temperature $T_\mathrm{m}$ corresponding roughly to the temperature of the maximum in the susceptibility $T_{\chi_\mathrm{max}}$ and coherent skew scattering at lower temperatures. The discontinuous field dependence of both, $S(H)$ and the ordinary Hall coefficient $R_0$, at $H_\mathrm{m}$ and at low temperature, provides evidence of a change in the band structure at the Fermi level., Comment: 5 figures in the main text; 9 figures in the supplemental material
Published: 2020
Full Text: View/download PDF

4. Anisotropy of the Upper Critical Field in the Heavy-Fermion Superconductor UTe2 under Pressure

Author: Knebel, Georg, Kimata, Motoi, Vališka, Michal, Honda, Fuminori, Li, Dexin, Braithwaite, Daniel, Lapertot, Gérard, Knafo, William, Pourret, Alexandre, Sato, Yoshiki J., Shimizu, Yusei, Kihara, Takumi, Brison, Jean-Pascal, Flouquet, Jacques, and Aoki, Dai
Subjects: Condensed Matter - Strongly Correlated Electrons
Abstract: We studied the anisotropy of the superconducting upper critical field $H_{\rm c2}$ in the heavy-fermion superconductor UTe$_2$ under hydrostatic pressure by magnetoresistivity measurements. In agreement with previous experiments we confirm that superconductivity disappears near a critical pressure $p_{\rm c} \approx 1.5$~GPa, and a magnetically ordered state appears. The unusual $H_{\rm c2}(T)$ at low temperatures for $H \parallel a$ suggests that the multiple superconducting phases which appear under pressure have quite different $H_{\rm c2}$. For a field applied along the hard magnetization $b$ axis $H_{\rm c2} (0)$ is glued to the metamagnetic transition $H_{\rm m}$ which is suppressed near $p_{\rm c}$. The suppression of $H_{\rm m}$ with pressure follows the decrease of temperature $T_{\chi}^{\rm max}$, at the maximum in the susceptibility along $b$. The strong reinforcement of $H_{\rm c2}$ at ambient pressure for $H \parallel b$ above 16~T is rapidly suppressed under pressure due to the increase of $T_{\rm sc}$ and the decrease of $H_{\rm m}$. The change in the hierarchy of the anisotropy of $H_{\rm c2}(0)$ on approaching $p_{\rm c}$ points out that the $c$ axis becomes the hard magnetization axis., Comment: 5 pages and 4 figures, supplemental material: 9 figures
Published: 2020
Full Text: View/download PDF

5. Competing pairing interactions responsible for the large upper critical field in a stoichiometric iron-based superconductor, CaKFe$_4$As$_4$

Author: Bristow, Matthew, Knafo, William, Reiss, Pascal, Meier, William, Canfield, Paul C., Blundell, Stephen J., and Coldea, Amalia I.
Subjects: Condensed Matter - Superconductivity, Condensed Matter - Strongly Correlated Electrons
Abstract: The upper critical field of multiband superconductors is an important quantity that can reveal the details about the nature of the superconducting pairing. Here we experimentally map out the complete upper critical field phase diagram of a stoichiometric superconductor, CaKFe$_4$As$_4$, up to 90T for different orientations of the magnetic field and at temperatures down to 4.2K. The upper critical fields are extremely large, reaching values close to ~3$T_c$ at the lowest temperature, and the anisotropy decreases dramatically with temperature leading to essentially isotropic superconductivity at 4.2K. We find that the temperature dependence of the upper critical field can be well described by a two-band model in the clean limit with band coupling parameters favouring intraband over interband interactions. The large Pauli paramagnetic effects together with the presence of the shallow bands is consistent with the stabilization of an FFLO state at low temperatures in this clean superconductor., Comment: to appear in Physical Review B (2020); 13 pages, 9 figures
Published: 2020
Full Text: View/download PDF

6. Field-reentrant superconductivity close to a metamagnetic transition in the heavy-fermion superconductor UTe$_2$

Author: Knebel, Georg, Knafo, William, Pourret, Alexandre, Niu, Qun, Vališka, Michal, Braithwaite, Daniel, Lapertot, Gérard, Nardone, Marc, Zitouni, Abdelaziz, Mishra, Sanu, Sheikin, Ilya, Seyfahrt, Gabriel, Brison, Jean-Pascal, Aoki, Dai, and Flouquet, Jacques
Subjects: Condensed Matter - Strongly Correlated Electrons
Abstract: We present a study of the upper critical field of the newly discovered heavy fermion superconductor UTe$_2$ by magnetoresistivity measurements in pulsed magnetic fields up to 60~T and static magnetic fields up to 35~T. We show that superconductivity survives up to the metamagnetic transition at $H_{\rm m} \approx 35$~T at low temperature. Above $H_{\rm m}$ superconductivity is suppressed. At higher temperature superconductivity is enhanced under magnetic field leading to reentrance of superconductivity or an almost temperature independent increase of $H_{\rm c2}$. By studying the angular dependence of the upper critical field close to the $b$ axis (hard magnetization axis) we show that the maximum of the reentrant superconductivity temperature is depinned from the metamagnetic field. A key ingredient for the field-reinforcement of superconductivity on approaching $H_{\rm m}$ appears to be an immediate interplay with magnetic fluctuations and a possible Fermi-surface reconstruction., Comment: 5 pages + Supplemental Material, accepted for publication in J. Phys. Soc. Jpn
Published: 2019
Full Text: View/download PDF

7. Magnetic-Field-Induced Phenomena in the Paramagnetic Superconductor UTe$_{2}$

Author: Knafo, William, Vališka, Michal, Braithwaite, Daniel, Lapertot, Gérard, Knebel, Georg, Pourret, Alexandre, Brison, Jean-Pascal, Flouquet, Jacques, and Aoki, Dai
Subjects: Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity
Abstract: We present magnetoresistivity measurements on the heavy-fermion superconductor UTe$_{2}$ in pulsed magnetic fields $\mu_0H$ up to 68~T and temperatures $T$ from 1.4 to 80~K. Magnetic fields applied along the three crystallographic directions $\mathbf{a}$ (easy magnetic axis), $\mathbf{b}$, and $\mathbf{c}$ (hard magnetic axes), are found to induce different phenomena - depending on the field direction - beyond the low-field suppression of the superconducting state. For $\mathbf{H}\parallel\mathbf{a}$, a broad anomaly in the resistivity is observed at $\mu_0H^*\simeq10$~T and $T = 1.4$~K. For $\mathbf{H}\parallel\mathbf{c}$, no magnetic transition nor crossover are observed. For $\mathbf{H}\parallel\mathbf{b}$, a sharp first-order-like step in the resistivity indicates a metamagnetic transition at the field $\mu_0H_m \simeq 35$~T. When the temperature is raised signature of first-order metamagnetism is observed up to a critical endpoint at $T_{CEP}\simeq7$~K. At higher temperatures a crossover persists up to 28~K, i.e., below the temperature $T_\chi^{max} = 35$~K where the magnetic susceptibility is maximal. A sharp maximum in the Fermi-liquid quadratic coefficient $A$ of the low-temperature resistivity is found at $H_m$. It indicates an enhanced effective mass associated with critical magnetic fluctuations, possibly coupled with a Fermi surface instability. Similarly to the URhGe case, we show that UTe$_{2}$ is a candidate for field-induced reentrant superconductivity in the proximity of $H_m$., Comment: 5 pages, 4 Figures, to be published in the Journal of the Physical Society of Japan includes Supplementary Materials (15 pages, 11 Figures)
Published: 2019
Full Text: View/download PDF

8. 40-tesla pulsed-field cryomagnet for single crystal neutron diffraction

Author: Duc, Fabienne, Tonon, Xavier, Billette, Julien, Rollet, Bertrand, Knafo, William, Bourdarot, Frédéric, Béard, Jérome, Mantegazza, Frédéric, Longuet, Benjamin, Lorenzo, Jose-Emilio, Lelièvre-Berna, Eddy, Frings, Paul, and Regnault, Louis-Pierre
Subjects: Physics - Instrumentation and Detectors, Condensed Matter - Strongly Correlated Electrons
Abstract: We present the first long-duration and high duty cycle 40-tesla pulsed-field cryomagnet addressed to single crystal neutron diffraction experiments at temperatures down to 2 K. The magnet produces a horizontal field in a bi-conical geometry, $\pm$15 and $\pm$30{\deg} upstream and downstream of the sample, respectively. Using a 1.15MJ mobile generator, magnetic field pulses of 100 ms length are generated in the magnet, with a rise time of 23 ms and a repetition rate of 6-7 pulses per hour at 40 T. The setup was validated for neutron diffraction on the CEA-CRG three-axis spectrometer IN22 at the ILL., Comment: 7 pages, 8 figures
Published: 2018
Full Text: View/download PDF

9. Angular Dependence of the High-Magnetic-Field Phase Diagram of URu2Si2

Author: Scheerer, Gernot W., Knafo, William, Aoki, Dai, and Flouquet, Jacques
Subjects: Condensed Matter - Strongly Correlated Electrons
Abstract: We present measurements of the magnetoresistivity RHOxx of URu2Si2 single crystals in high magnetic fields up to 60 T and at temperatures from 1.4 K to 40 K. Different orientations of the magnetic field have been investigated permitting to follow the dependence on Q of all magnetic phase transitions and crossovers, where Q is the angle between the magnetic field and the easy-axis c. We find out that all magnetic transitions and crossovers follow a simple 1/cos(Q) -law, indicating that they are controlled by the projection of the field on the c-axis.
Published: 2012
Full Text: View/download PDF

10. Decoupling between Field-instabilities of Antiferromagnetism and Pseudo-metamagnetism in Rh-doped CeRu2Si2 Kondo Lattice

Author: Aoki, Dai, Paulsen, Carley, Kotegawa, Hisashi, Hardy, Frederic, Meingast, Christoph, Haen, Pierre, Boukahil, Mounir, Knafo, William, Ressouche, Eric, Raymond, Stephane, and Flouquet, Jacques
Subjects: Condensed Matter - Strongly Correlated Electrons
Abstract: Doping Kondo lattice system CeRu2Si2 with Rh-8% (Ce(Ru0.92Rh0.08)2Si2) leads to drastic consequences due to the mismatch of the lattice parameters between CeRu2Si2 and CeRh2Si2. A large variety of experiments clarifies the unusual properties of the ground state induced by the magnetic field from longitudinal antiferromagnetic (AF) mode at H = 0 to polarized paramagnetic phase in very high magnetic field. The separation between AF phase, paramagnetic phase and polarized paramagnetic phase varying with temperature, magnetic field and pressure is discussed on the basis of the experiments down to very low temperature. Similarities and differences between Rh and La substituted alloys are discussed with emphasis on the competition between transverse and longitudinal AF modes, and ferromagnetic fluctuations., Comment: 10 pages, 21 figures, accepted for publication in J. Phys. Soc. Jpn
Published: 2012
Full Text: View/download PDF

11. Field-induced Phenomena in Ferromagnetic Superconductors UCoGe and URhGe

Author: Aoki, Dai, Taupin, Mathieu, Paulsen, Carley, Hardy, Frederic, Taufour, Valentin, Kotegawa, Hisashi, Hassinger, Elena, Malone, Liam, Matsuda, Tatsuma D., Miyake, Atsushi, Sheikin, Ilya, Knafo, William, Knebel, Georg, Howald, Ludovic, Brison, Jean-Pascal, and Flouquet, Jacques
Subjects: Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity
Abstract: We review our recent studies on ferromagnetic superconductors, UGe2, URhGe and UCoGe, where the spin-triplet state with the so-called equal spin pairing is realized. We focus on experimental results of URhGe and UCoGe in which the superconductivity occurs already at ambient pressure. The huge upper critical field Hc2 on UCoGe for the field along the hard magnetization axis (b-axis) is confirmed by the AC susceptibility measurements by the fine tuning of field angle. Contrary to the huge Hc2 along the hard-magnetization axis, Hc2 along the easy-magnetization axis (c-axis) is relatively small in value. However, the initial slope of Hc2, namely dHc2/dT (H -> 0) both in UCoGe and in URhGe indicates the large value, which can be explained by the magnetic domain effect detected in the magnetization measurements. The specific heat measurements using a high quality single crystal of UCoGe demonstrate the bulk superconductivity, which is extended under magnetic field for the field along c-axis., Comment: 6 pages, 4 figures, proceedings of TOKIMEKI2011, to be published in J. Phys. Soc. Jpn. Suppl
Published: 2012
Full Text: View/download PDF

12. Evidence for Anisotropic Vortex Dynamics and Pauli Limitation in the Upper Critical Field of FeSe1-xTex

Author: Braithwaite, Daniel, Lapertot, Gérard, Knafo, William, and Sheikin, Ilya
Subjects: Condensed Matter - Superconductivity
Abstract: We have determined HC2(T) for FeSe1-xTex (x=0.52) single crystals using resistivity measurements at high static and pulsed magnetic field, as well as specific heat measurements up to 9T. We find that the significant anisotropy of the initial slope of HC2(T) determined from resistivity measurements, is not present when HC2 is determined from the specific heat results. This suggests that the thermodynamic upper critical field is almost isotropic, and that anisotropic vortex dynamics play a role. Further evidence of anisotropic vortex dynamics is found in the behaviour in pulsed field. We also find that Pauli limiting must be included in order to fit the temperature dependence of HC2, indicating probably higher effective mass in FeSe1-xTex than in other Fe superconductors.
Published: 2010
Full Text: View/download PDF

13. Quenched nematic criticality and two superconducting domes in an iron-based superconductor

Author: Reiss, Pascal, Graf, David, Haghighirad, Amir A., Knafo, William, Drigo, Loïc, Bristow, Matthew, Schofield, Andrew J., and Coldea, Amalia I.
Published: 2020
Full Text: View/download PDF

14. Evolution of the low-temperature Fermi surface of superconducting FeSe1−xSx across a nematic phase transition

Author: Coldea, Amalia I., Blake, Samuel F., Kasahara, Shigeru, Haghighirad, Amir A., Watson, Matthew D., Knafo, William, Choi, Eun Sang, McCollam, Alix, Reiss, Pascal, Yamashita, Takuya, Bruma, Mara, Speller, Susannah C., Matsuda, Yuji, Wolf, Thomas, Shibauchi, Takasada, and Schofield, Andrew J.
Published: 2019
Full Text: View/download PDF

15. COVID-19: Monitoring the propagation of the first waves of the pandemic

Author: Knafo William
Subjects: asia, australia, belgium, brazil, czech republic, china, covid-19, epidemic, epidemic wave, epidemiology, europe, france, germany, greece, hong kong, immunity, india, iran, israel, italy, japan, lockdown, mexico, morbidity, morocco, mortality, the netherlands, nigeria, norway, pandemic, phenomenological description, philippines, portugal, protection, resurging epidemic waves, russia, sars-cov-2, sepsis, singapore, south korea, scandinavia, spain, south africa, sweden, switzerland, taiwan, western europe, united kingdom, usa, virus, Medicine, Science
Abstract: Introduction: A phenomenological approach is proposed to monitor the propagation of the first waves of the COVID-19 pandemic. Method: A large set of data collected during the first months of 2020 is compiled into a series of semi-logarithmic plots, for a selection of 32 countries from the five continents. Results: Three regimes are identified in the propagation of an epidemic wave: a pre-epidemic regime 1, an exponential-growth regime 2, and a resorption regime 3. A two-parameters scaling of the first-wave death variation reported in China is used to fit the first-wave data reported in other countries. Comparison is made between the propagation of the pandemic in different countries, which are classified into four groups, from Group A where the pandemic first waves were contained efficiently, to Group D where the pandemic first waves widely spread. All Asian countries considered here, where fast and efficient measures have been applied, are in Group A. Group D is composed of Western-European countries and the United States of America (USA), where late decisions and confused political communication (pandemic seriousness, protection masks, herd immunity, etc.) led to a large number of deaths. Discussion: The threat of resurging epidemic waves following a lift of lockdown measures is discussed. The results obtained in Asian countries from group A, as Hong Kong and South Korea, are highlighted, and the measures taken there are presented as examples that other countries may follow.
Published: 2020
Full Text: View/download PDF

16. Heavy fermions in a high magnetic field

Author: Aoki, Dai, Knafo, William, and Sheikin, Ilya
Published: 2013
Full Text: View/download PDF

17. Magnetism of Heavy-Fermion Metals

Author: Knafo, William, primary
Published: 2022
Full Text: View/download PDF

18. Feedback of Superconductivity on the Magnetic Excitation Spectrum of UTe2

Author: Raymond, Stéphane, primary, Knafo, William, additional, Knebel, Georg, additional, Kaneko, Koji, additional, Brison, Jean-Pascal, additional, Flouquet, Jacques, additional, Aoki, Dai, additional, and Lapertot, Gérard, additional
Published: 2021
Full Text: View/download PDF

19. Field-Induced Superconductivity near the Superconducting Critical Pressure in UTe2

Author: Aoki, Dai, primary, Kimata, Motoi, additional, Sato, Yoshiki J., additional, Knebel, Georg, additional, Honda, Fuminori, additional, Nakamura, Ai, additional, Li, Dexin, additional, Homma, Yoshiya, additional, Shimizu, Yusei, additional, Knafo, William, additional, Braithwaite, Daniel, additional, Vališka, Michal, additional, Pourret, Alexandre, additional, Brison, Jean-Pascal, additional, and Flouquet, Jacques, additional
Published: 2021
Full Text: View/download PDF

20. Further Analysis of the Quantum Critical Point of Ce1-x La x Ru2Si2

Author: Raymond, Stéphane, Knafo, William, Flouquet, Jacques, and Lejay, Pascal
Published: 2007
Full Text: View/download PDF

21. Monitoring the propagation of COVID-19-pandemic first waves

Author: Knafo, William
Subjects: Geography, Coronavirus disease 2019 (COVID-19), Scale (social sciences), media_common.quotation_subject, Development economics, Pandemic, Asian country, Political communication, China, Seriousness, media_common, Herd immunity
Abstract: A phenomenological approach is proposed to monitor the propagation of the COVID-19-pandemic first waves. A large set of data collected at a worldwide scale during the first months of 2020 is compiled into series of semi-logarithmic plots, for a selection of thirty-two countries from the five continents. Three regimes are identified in the propagation of an epidemic wave: a pre-epidemic regime 1, an exponential-growth regime 2, and a resorption regime 3. A two-parameters scaling of the first-wave death variation reported in China is used to fit those reported in other countries. Comparison is made between the propagation of the pandemic in different countries, which are classified in four groups, from group A where the pandemic first waves were contained efficiently, to group D where the pandemic first waves widely spread. Group A is mainly composed of Asian countries, where fast and efficient measures have been applied. Group D is composed of Western-Europe countries and the United States of America, where late decisions and confused political communication (pandemic seriousness, protection masks, herd immunity etc.) led to significant death tolls. The threat of large resurging epidemic waves after a hasty lockdown lift is discussed, in particular for the countries from group D, where the number of contagious people remained high in the beginning of May 2020. The situation is opposite in Asian countries from group A, where the number of contagious people was successfully maintained to a low level. In particular, the results obtained by Hong Kong and South Korea are highlighted, and the measures taken there are presented as virtuous examples that other countries may follow.
Published: 2020
Full Text: View/download PDF

22. Competing pairing interactions responsible for the large upper critical field in a stoichiometric iron-based superconductor CaKFe 4 As 4

Author: Bristow, Matthew, Knafo, William, Reiss, Pascal, Meier, William, Canfield, Paul, Blundell, Stephen, Coldea, Amalia, Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)
Subjects: Condensed Matter::Superconductivity, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat]
Abstract: International audience; The upper critical field of multiband superconductors is an important quantity that can reveal details about the nature of the superconducting pairing. Here we experimentally map out the complete upper-critical-field phase diagram of a stoichiometric superconductor, CaKFe 4 As 4 , up to 90 T for different orientations of the magnetic field and at temperatures down to 4.2 K. The upper critical fields are extremely large, reaching values close to ∼3 T c at the lowest temperature, and the anisotropy decreases dramatically with temperature, leading to essentially isotropic superconductivity at 4.2 K. We find that the temperature dependence of the upper critical field can be well described by a two-band model in the clean limit with band-coupling parameters favoring intraband over interband interactions. The large Pauli paramagnetic effects together with the presence of the shallow bands is consistent with the stabilization of an FFLO state at low temperatures in this clean superconductor.
Published: 2020
Full Text: View/download PDF

23. Anisotropy of the Upper Critical Field in the Heavy-Fermion Superconductor UTe2 under Pressure

Author: Knebel, Georg, primary, Kimata, Motoi, additional, Vališka, Michal, additional, Honda, Fuminori, additional, Li, DeXin, additional, Braithwaite, Daniel, additional, Lapertot, Gérard, additional, Knafo, William, additional, Pourret, Alexandre, additional, Sato, Yoshiki J., additional, Shimizu, Yusei, additional, Kihara, Takumi, additional, Brison, Jean-Pascal, additional, Flouquet, Jacques, additional, and Aoki, Dai, additional
Published: 2020
Full Text: View/download PDF

24. Monitoring the propagation of COVID-19-pandemic first waves

Author: Knafo, William, primary
Published: 2020
Full Text: View/download PDF

25. Quenched nematic criticality separating two superconducting domes in an iron-based superconductor under pressure

Author: Reiss, Pascal, Graf, David, Haghighirad, Amir, Knafo, William, Drigo, Loïc, Bristow, Matthew, Schofield, Andrew, Coldea, Amalia, Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)
Subjects: Superconductivity (cond-mat.supr-con), [PHYS]Physics [physics], Condensed Matter::Soft Condensed Matter, Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons, Strongly Correlated Electrons (cond-mat.str-el), Condensed Matter - Superconductivity, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat]
Abstract: The nematic electronic state and its associated nematic critical fluctuations have emerged as potential candidates for superconducting pairing in various unconventional superconductors. However, in most materials their coexistence with other magnetically-ordered phases poses significant challenges in establishing their importance. Here, by combining chemical and hydrostatic physical pressure in FeSe$_{0.89}$S$_{0.11}$, we provide a unique access to a clean nematic quantum phase transition in the absence of a long-range magnetic order. We find that in the proximity of the nematic phase transition, there is an unusual non-Fermi liquid behavior in resistivity at high temperatures that evolves into a Fermi liquid behaviour at the lowest temperatures. From quantum oscillations in high magnetic fields, we trace the evolution of the Fermi surface and electronic correlations as a function of applied pressure. We detect experimentally a Lifshitz transition that separates two distinct superconducting regions: one emerging from the nematic electronic phase with a small Fermi surface and strong electronic correlations and the other one with a large Fermi surface and weak correlations that promotes nesting and stabilization of a magnetically-ordered phase at high pressures. The lack of mass divergence suggests that the nematic critical fluctuations are quenched by the strong coupling to the lattice. This establishes that superconductivity is not enhanced at the nematic quantum phase transition in the absence of magnetic order., 4 figures, 9 pages
Published: 2019
Full Text: View/download PDF

26. High magnetic field behavior of NbFe2

Author: D., Rauch, N., Steinki, Knafo, William, C., Pfleiderer, W.J., Duncan, F.M., Grosche, Süllow, S., Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2019

27. URu2Si2 under intense magnetic fields: From hidden order to spin-density wave

Author: Knafo , William, Dai , Aoki, G.W. , Scheerer, Duc , F., F. , Bourdarot, K. , Kuwahara, H. , Nojiri, Regnault , L.P., Flouquet , J., Laboratoire national des champs magnétiques intenses - Toulouse ( LNCMI ), Centre National de la Recherche Scientifique ( CNRS ) -Institut National des Sciences Appliquées - Toulouse ( INSA Toulouse ), and Institut National des Sciences Appliquées ( INSA ) -Institut National des Sciences Appliquées ( INSA )
Subjects: [ PHYS.COND.CM-S ] Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2019

28. 40-Tesla pulsed-eld cryomagnet for single crystal neutron diffraction

Author: Duc, F., Tonon, X., BILLETTE, Julien, Rollet, B., Knafo, William, Bourdarot, Frédéric, Beard, Jerome, Mantegazza, F., Longuet, B., J.E., Lorenzo, Lelievre-Berna, E., Frings, P., Regnault, L.P., Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), and Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2019

29. Quenched nematic criticality and two superconducting domes in an iron-based superconductor

Author: Pascal, Reiss, David, Graf, Amir A., Haghighirad, Knafo, William, Drigo, Loïc, Matthew, Bristow, Andrew J., Schoeld, Amalia I., Coldea, Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), and Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)
Subjects: [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2019

30. URu$_2$Si$_2$ under intense magnetic fields: From hidden order to spin-density wave

Author: Knafo, William, Aoki, D., Scheerer, Gernot, Duc, F., Bourdarot, Frederic, Kuwahara, K., Nojiri, H., Regnault, L.-P., Flouquet, J., Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Instrumentation, Material and Correlated Electrons Physics (IMAPEC), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Magnétisme et Diffusion Neutronique (MDN), Modélisation et Exploration des Matériaux (MEM), Ibaraki University, Tohoku University [Sendai], Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), ANR-11-IDEX-0002,UNITI,Université Fédérale de Toulouse(2011), ANR-10-BLAN-0431,MAGFINS,Diffusion des neutrons sous champ magnétique intense(2010), ANR-10-IDEX-0002,UNISTRA,Par-delà les frontières, l'Université de Strasbourg(2010), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), and Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)
Subjects: Condensed Matter - Strongly Correlated Electrons, high magnetic field, spin-density wave, Strongly Correlated Electrons (cond-mat.str-el), URu$_2$Si$_2$, heavy fermions, Fermi surface, hidden order, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], FOS: Physical sciences, Condensed Matter::Strongly Correlated Electrons, [PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el]
Abstract: A review of recent state-of-the-art pulsed field experiments performed on URu$_2$Si$_2$ under a magnetic field applied along its easy magnetic axis $\mathbf{c}$ is given. Resistivity, magnetization, magnetic susceptibility, Shubnikov-de Haas, and neutron diffraction experiments are presented, permitting to emphasize the relationship between Fermi surface reconstructions, the destruction of the hidden-order and the appearance of a spin-density wave state in a high magnetic field., 14 pages, 2 figures
Published: 2018
Full Text: View/download PDF

31. Three-dimensional critical phase diagram of the Ising antiferromagnet CeRh2Si2 under intense magnetic field and pressure

Author: Knafo, William, R., Settai, D., Braithwaite, S., Kurahashi, D., Aoki, And J., Flouquet, Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2018

32. Quenched nematic criticality and two superconducting domes in an iron-based superconductor

Author: Reiss, Pascal, primary, Graf, David, additional, Haghighirad, Amir A., additional, Knafo, William, additional, Drigo, Loïc, additional, Bristow, Matthew, additional, Schofield, Andrew J., additional, and Coldea, Amalia I., additional
Published: 2019
Full Text: View/download PDF

33. Field-Reentrant Superconductivity Close to a Metamagnetic Transition in the Heavy-Fermion Superconductor UTe2

Author: Knebel, Georg, primary, Knafo, William, additional, Pourret, Alexandre, additional, Niu, Qun, additional, Vališka, Michal, additional, Braithwaite, Daniel, additional, Lapertot, Gérard, additional, Nardone, Marc, additional, Zitouni, Abdelaziz, additional, Mishra, Sanu, additional, Sheikin, Ilya, additional, Seyfarth, Gabriel, additional, Brison, Jean-Pascal, additional, Aoki, Dai, additional, and Flouquet, Jacques, additional
Published: 2019
Full Text: View/download PDF

34. Magnetic-Field-Induced Phenomena in the Paramagnetic Superconductor UTe2

Author: Knafo, William, primary, Vališka, Michal, additional, Braithwaite, Daniel, additional, Lapertot, Gérard, additional, Knebel, Georg, additional, Pourret, Alexandre, additional, Brison, Jean-Pascal, additional, Flouquet, Jacques, additional, and Aoki, Dai, additional
Published: 2019
Full Text: View/download PDF

35. Field-Induced Superconductivity near the Superconducting Critical Pressure in UTe2.

Author: Dai Aoki, Motoi Kimata, Sato, Yoshiki J., Knebel, Georg, Fuminori Honda, Ai Nakamura, Dexin Li, Yoshiya Homma, Yusei Shimizu, Knafo, William, Braithwaite, Daniel, Vališka, Michal, Pourret, Alexandre, Brison, Jean-Pascal, and Flouquet, Jacques
Abstract: We report the magnetoresistance under pressure in the novel spin-triplet superconductor UTe2 close to the critical pressure Pc, where the superconducting phase terminates, for field along the three a, b, and c-axes in the orthorhombic structure. The superconducting phase for H k a-axis just below Pc shows a field-reentrant behavior due to the competition with the emergence of magnetic order at low fields. The upper critical field Hc2 for H k c-axis shows a quasi-vertical increase in the H-T phase diagram just below Pc, indicating that superconductivity is reinforced by the strong fluctuations which persist even at high fields above 20 T. Increasing pressure leads to the disappearance of superconductivity at zero field with the emergence of magnetic order. Surprisingly, field-induced superconductivity is observed at high fields, where a spin-polarized state is realized due to the suppression of the magnetic ordered phases; the spin-polarized state is favorable for superconductivity, whereas the magnetic ordered phase at low field seems to be unfavorable. The huge Hc2 in the spin-polarized state seems to imply a spin-triplet state. Contrary to the a- and c-axes, no field-reinforcement of superconductivity occurs for magnetic field along the b-axis. We compare the results with the field-reentrant superconductivity above the metamagnetic field, Hm for the field direction tilted by ∼30 deg from b to caxis at ambient pressure as well as the field-reentrant (-reinforced) superconductivity in ferromagnetic superconductors, URhGe and UCoGe [ABSTRACT FROM AUTHOR]
Published: 2021
Full Text: View/download PDF

36. Evolution of the low-temperature Fermi surface of superconducting FeSe1−xSx across a nematic phase transition

Author: Coldea, A.I., Blake, Samuel F., Kasahara, Shigeru, Haghighirad, Amir A., Watson, Matthew D., Knafo, William, Choi, Eun Sang, McCollam, A., Reiss, Pascal, Yamashita, Takuya, Bruma, Mara, Speller, Susannah C., Matsuda, Yuji, Wolf, Thomas, Shibauchi, Takasada, Schofield, Andrew J., Coldea, A.I., Blake, Samuel F., Kasahara, Shigeru, Haghighirad, Amir A., Watson, Matthew D., Knafo, William, Choi, Eun Sang, McCollam, A., Reiss, Pascal, Yamashita, Takuya, Bruma, Mara, Speller, Susannah C., Matsuda, Yuji, Wolf, Thomas, Shibauchi, Takasada, and Schofield, Andrew J.
Abstract: Contains fulltext : 214812.pdf (publisher's version ) (Open Access)
Published: 2019

37. Anisotropy of the Upper Critical Field in the Heavy-Fermion Superconductor UTe2 under Pressure.

Author: Knebel, Georg, Kimata, Motoi, Vališka, Michal, Honda, Fuminori, Li, DeXin, Braithwaite, Daniel, Lapertot, Gérard, Knafo, William, Pourret, Alexandre, Sato, Yoshiki J., Shimizu, Yusei, Kihara, Takumi, Brison, Jean-Pascal, Flouquet, Jacques, and Aoki, Dai
Abstract: We studied the anisotropy of the superconducting upper critical field Hc2 in the heavy-fermion superconductor UTe2 under hydrostatic pressure by magnetoresistivity measurements. In agreement with previous experiments we confirm that superconductivity disappears near a critical pressure pc ≈ 1.5 GPa, and a magnetically ordered state appears. The unusual Hc2(T) at low temperatures for $H\parallel a$ suggests that the multiple superconducting phases which appear under pressure have quite different Hc2. For a field applied along the hard magnetization b axis Hc2(0) is glued to the metamagnetic transition Hm, which is suppressed near pc. The suppression of Hm with pressure follows the decrease of temperature $T_{\chi }^{\text{max}}$ , at the maximum in the susceptibility along b. The strong reinforcement of Hc2 at ambient pressure for $H\parallel b$ above 16 T is rapidly suppressed under pressure due to the increase of Tsc and the decrease of Hm. The change in the hierarchy of the anisotropy of Hc2(0) on approaching pc points out that the c axis becomes the hard magnetization axis. [ABSTRACT FROM AUTHOR]
Published: 2020
Full Text: View/download PDF

38. Specific heat of the Kagomé mixed compounds (Co 1−xNi x) 3V 2O 8

Author: Zhang, Qin, Knafo, William, Grube, Kai, Löhneysen, Hilbert V., Meingast, Christoph, and Wolf, Thomas
Published: 2008
Full Text: View/download PDF

39. Dichotomy between Attractive and Repulsive Tomonaga-Luttinger Liquids in Spin Ladders

Author: Knafo , William, Ballon , Géraldine, Laboratoire national des champs magnétiques intenses - Toulouse ( LNCMI ), Institut National des Sciences Appliquées - Toulouse ( INSA Toulouse ), and Institut National des Sciences Appliquées ( INSA ) -Institut National des Sciences Appliquées ( INSA ) -Centre National de la Recherche Scientifique ( CNRS )
Subjects: [ PHYS.COND.CM-S ] Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2016

40. Study of the magnetic fluctuations of heavy fermions systems by inelastic neutron scattering

Author: Knafo, William, Magnétisme et Diffusion Neutronique (MDN), Modélisation et Exploration des Matériaux (MEM), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Joseph-Fourier - Grenoble I, Regnault Louis-Pierre(regnault@ill.fr), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), and Knafo, William
Subjects: Inelastic Neutron Scattering, Criticality, Heavy Fermions, Réseau Kondo, Magnetic Instability, Kondo Lattice, Lois d'Echelles, Diffusion Inélastique des Neutrons, Fermions Lourds, Transition de Phase Quantique, Magnetic Fluctuations, Criticalité, Scaling Laws, Instabilité Magnétique, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], [PHYS.PHYS.PHYS-DATA-AN] Physics [physics]/Physics [physics]/Data Analysis, Statistics and Probability [physics.data-an], Fluctuations Magnétiques, [PHYS.COND] Physics [physics]/Condensed Matter [cond-mat], [PHYS.PHYS.PHYS-DATA-AN]Physics [physics]/Physics [physics]/Data Analysis, Statistics and Probability [physics.data-an], Quantum Phase Transition
Abstract: In the present work, inelastic neutron scattering has been performed to study the magnetic excitations of the heavy fermions systems Ce(1-x)La(x)Ru2Si2 and CeIn(3-x)Sn(x). Those systems are characterized by a quantum phase transition (at T = 0) between a magnetically ordered ground state and a Fermi liquid paramagnetic ground state. The first experimental part is devoted to the system Ce(1-x)La(x)Ru2Si2. A detailed study of the temperature dependence of the magnetic fluctuations is carried out for the compound of critical concentration xc and for the paramagnetic compound of concentration x = 0. We find i) that the magnetic fluctuations saturate at low temperatures, and ii) that the dynamical susceptibility, which corresponds to those fluctuations, follows a high temperature E/T^b scaling law with b < 1. Such results do not enter the framework of quantum phase transitions theories, since i) a divergence of the spin fluctuations is expected, and ii) a E/T^b scaling law can only occur with b > 1 in those theories. A study of the ordered compounds x > xc permits to conclude that the antiferromagnetic fluctuations are critical and that they govern the transition, even if they do not diverge at the magnetic instability. The second part concerns the system CeIn(3-x)Sn(x). A study of the excitations spectra of CeIn3 illustrates the duality of heavy fermions systems : well-defined spin waves are a manifestation of the localized character of the f electrons, while the broadening the crystal field excitations is due to their itinerant character. A study of the magnetic fluctuations of the critical compound of concentration xc=0.6 seems also to indicate their saturation below 10 K., Dans le travail présenté ici, la diffusion inélastique des neutrons est utilisée pour étudier les excitations magnétiques des systèmes à fermions lourds Ce(1-x)La(x)Ru2Si2 et CeIn(3-x)Sn(x). Une première partie expérimentale est consacrée au système Ce(1-x)La(x)Ru2Si2. Les fluctuations magnétiques du composé de concentration critique xc = 7.5 % et du composé paramagnétique de concentration x = 0 % sont d'abord étudiées. On obtient i) que les fluctuations magnétiques de ces deux alliages saturent aux basses températures, et ii) qu'aux hautes températures la susceptibilité dynamique suit une loi d'échelle en E/T^b avec b < 1. Ces résultats ne rentrent pas dans le cadre des théories sur les transitions de phase quantiques : en effet, i) ces théories prévoient que les fluctuations divergent à la transition, et ii) seuls des exposants b > 1 peuvent être obtenus dans de tels modèles. Une étude des composés ordonnés de concentrations x > xc permet de conclure que les fluctuations corrélées antiferromagnétiquement sont les fluctuations critiques qui gouvernent la transition de phase quantique, bien qu'elles ne divergent pas à l'instabilité magnétique. La deuxième partie consiste en l'étude du système CeIn(3-x)Sn(x). Le spectre des excitations de CeIn3 illustre la dualité des systèmes à fermions lourds : le caractère localisé des électrons f se manifeste par des ondes de spin très bien définies alors que leur caractère itinérant se traduit par un fort élargissement de l'excitation de champ cristallin. Une étude du spectre des excitations d'une poudre du composé de concentration critique xc = 0.6 semble par ailleurs indiquer que les fluctuations magnétiques saturent aux basses températures.
Published: 2004

41. Fermi surface in the hidden-order state of URu2Si2 under intense pulsed magnetic fields up to 81 T

Author: Scheerer, Gernot, Knafo, William, Aoki, D., Nardone, Marc, Zitouni, Abdelaziz, J. B., Eard, Billette, Julien, Barata, J., Jaudet, C., Suleiman, M., Frings, P., Drigo, Loïc, Audouard, Alain, D. Matsuda, T., Pourret, A., Knebel, G., Flouquet, J., Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), Instrumentation, Material and Correlated Electrons Physics (IMAPEC), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire National des Champs Magnétiques Pulsés (LNCMP), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Laboratoire de Physique Quantique (LPQ), Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], Condensed Matter - Strongly Correlated Electrons, Strongly Correlated Electrons (cond-mat.str-el), FOS: Physical sciences, ComputingMilieux_MISCELLANEOUS
Abstract: We present measurements of the resistivity $\rho_{x,x}$ of URu2Si2 high-quality single crystals in pulsed high magnetic fields up to 81~T at a temperature of 1.4~K and up to 60~T at temperatures down to 100~mK. For a field \textbf{H} applied along the magnetic easy-axis \textbf{c}, a strong sample-dependence of the low-temperature resistivity in the hidden-order phase is attributed to a high carrier mobility. The interplay between the magnetic and orbital properties is emphasized by the angle-dependence of the phase diagram, where magnetic transition fields and crossover fields related to the Fermi surface properties follow a 1/$\cos\theta$-law, $\theta$ being the angle between \textbf{H} and \textbf{c}. For $\mathbf{H}\parallel\mathbf{c}$, a crossover defined at a kink of $\rho_{x,x}$, as initially reported in [Shishido et al., Phys. Rev. Lett. \textbf{102}, 156403 (2009)], is found to be strongly sample-dependent: its characteristic field $\mu_0H^*$ varies from $\simeq20$~T in our best sample with a residual resistivity ratio RRR of $225$ to $\simeq25$~T in a sample with a RRR of $90$. A second crossover is defined at the maximum of $\rho_{x,x}$ at the sample-independent characteristic field $\mu_0H_{\rho,max}^{LT}\simeq30$~T. Fourier analyzes of SdH oscillations show that $H_{\rho,max}^{LT}$ coincides with a sudden modification of the Fermi surface, while $H^*$ lies in a regime where the Fermi surface is smoothly modified. For $\mathbf{H}\parallel\mathbf{a}$, i) no phase transition is observed at low temperature and the system remains in the hidden-order phase up to 81~T, ii) quantum oscillations surviving up to 7~K are related to a new and almost-spherical orbit - for the first time observed here - at the frequency $F_\lambda\simeq1400$~T and associated with a low effective mass $m^*_\lambda=(1\pm0.5)\cdot m_0$, and iii) no Fermi surface modification occurs up to 81~T., Comment: 11 pages, 8 figures
Published: 2014
Full Text: View/download PDF

42. Magnetic Structure of Phase II in U ( Ru 0.96 Rh 0.04 ) 2 Si 2 Determined by Neutron Diffraction under Pulsed High Magnetic Fields

Author: Kuwahara, K., Yoshii, S., Nojiri, H., Aoki, D., Knafo, William, Duc, F., Fabrèges, Xavier, Scheerer, Gernot, Frings, P., G.L.J.A., Rikken, Bourdarot, F., Regnault, L., Flouquet, J., Ibaraki University, Tohoku University [Sendai], Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Magnétisme et Diffusion Neutronique (MDN), Modélisation et Exploration des Matériaux (MEM), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de Cryophysique (LCP), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut Nanosciences et Cryogénie (INAC), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), and Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut Nanosciences et Cryogénie (INAC)
Subjects: [PHYS]Physics [physics], [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], PACS numbers: 71.27.+a, 74.70.Tx, 75.25.j, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Condensed Matter::Strongly Correlated Electrons
Abstract: International audience; We report neutron diffraction measurements on U(Ru0.96Rh0.04)2Si2 single crystal under pulsed high magnetic fields up to 30 T applied along the tetragonal c axis. The high-field experiments revealed that the field-induced phase II above 26 T corresponds to a commensurate up-up-down ferrimagnetic structure characterized by the wave vector q=(2/3,0,0) with the magnetic moments parallel to the c axis, which naturally explains the one-third magnetization plateau and the substantially changed Fermi surface in phase II. This a-axis modulated magnetic structure indicates that the phase II near the hidden order phase is closely related to the characteristic incommensurate magnetic fluctuations at Q1=(0.6,0,0) in the pure system URu2Si2, in contrast to the pressure-induced antiferromagnetic order at Q0=(1,0,0).
Published: 2013
Full Text: View/download PDF

43. Magnetic Structure of Phase II in U(Ru0:96Rh0:04)2Si2 Determined by Neutron Diff raction under Pulsed High Magnetic Fields

Author: Kuwahara, K., Yoshii, S., Nojiri, H., Aoki, D., Knafo, William, Duc, F., Fabrèges, Xavier, Scheerer, Gernot, Frings, P., G.L.J.A., Rikken, Bourdarot, F., Regnault, L.P., Flouquet, J., Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire National des Champs Magnétiques Pulsés (LNCMP), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), CEA, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), and Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)
Subjects: [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2013

44. Angular dependence of the high-magnetic- eld phase diagram of URu2Si2

Author: Scheerer, Gernot, Knafo, William, Aoki, D., J. Flouquet, And, Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2012

45. Complex magnetoelastic properties in the frustrated kagome-staircase compounds (Co1-xNix)3V2O8

Author: Zhang, Q., Knafo, William, Adelmann, P., Schweiss, P., Grube, K., Qureshi, Muhammad Nauman, Wolf, Th., Löhneysen, H. V., Meingast, C., Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire des Écoulements Géophysiques et Industriels [Grenoble] (LEGI), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], Condensed Matter::Strongly Correlated Electrons
Abstract: International audience; High-resolution heat-capacity and thermal-expansion measurements on single crystals of the kagome-staircase compounds (Co1−xNix)3V2O8 are presented. The parent compounds Co3V2O8 and Ni3V2O8 undergo a sequence of first- and second-order magnetic phase transitions. The low-temperature (T⩽40 K) magnetic entropy evolves monotonically with the doping content x from the full value expected for Ni2+ S=1 magnetic moments in Ni3V2O8 to only half the value expected for Co2+ S=3/2 moments in Co3V2O8. The thermal-expansion coefficients αi (i=a, b, and c) show a strong anisotropy for all (Co1−xNix)3V2O8 compounds. The low-temperature expansivities indicate that Co doping (Ni doping) yields changes similar to uniaxial pressures along a or b (c). Linear Grüneisen parameters Γi are extracted for the three main axes i and are found to exhibit a complex temperature and doping dependence. For each axis, Γi and αi exhibit a sign change at low temperature at the critical concentration xc≃0.25 where the incommensurate magnetic propagation vector changes. Our study motivates further investigations to understand how the multiple and complex parameters such as magnetic frustration, magnetic anisotropy, and mixture of S=1 and 3/2 ions affect the rich magnetoelastic properties of (Co1−xNix)3V2O8.
Published: 2011
Full Text: View/download PDF

46. Interplay of magnetism, Fermi surface reconstructions, and hidden-order in the heavy-fermion material URu$_2$Si$_2$

Author: Scheerer, Gernot, Knafo, William, Aoki, D., Ballon, Géraldine, Mari, A., Vignolles, David, J. Flouquet, And, Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], Condensed Matter - Strongly Correlated Electrons, Strongly Correlated Electrons (cond-mat.str-el), FOS: Physical sciences, Condensed Matter::Strongly Correlated Electrons, ComputingMilieux_MISCELLANEOUS
Abstract: URu$_2$Si$_2$ is surely one of the most mysterious of the heavy-fermion compounds. Despite more than twenty years of experimental and theoretical works, the order parameter of the transition at $T_0 = 17.5$ K is still unknown. The state below $T_0$ remains called "hidden-order phase" and the stakes are still to identify the energy scales driving the system to this phase. We present new magnetoresistivity and magnetization measurements performed on very-high-quality single crystals in pulsed magnetic fields up to 60 T. We show that the transition to the hidden-order state in URu$_2$Si$_2$ is initially driven by a high-temperature crossover at around 40-50 K, which is a fingerprint of inter-site electronic correlations. In a magnetic field $\mathbf{H}$ applied along the easy-axis $\bf{c}$, the vanishing of this high-temperature scale precedes the polarization of the magnetic moments, as well as it drives the destabilization of the hidden-order phase. Strongly impurity-dependent magnetoresistivity confirms that the Fermi surface is reconstructed below $T_0$ and is strongly modified in a high magnetic field applied along $\mathbf{c}$, i.e. at a sufficiently-high magnetic polarization. The possibility of a sharp crossover in the hidden-order state controlled by a field-induced change of the Fermi surface is pointed out., Comment: 10 pages, 6 figures, accepted in Physical Review B
Published: 2011
Full Text: View/download PDF

47. Ferromagnetism and Superconductivity in Uranium Compounds

Author: Aoki, D., Taupin, M., Paulsen, C., Hardy, F., Taufour, V., Kotegawa, H., Hassinger, E., Malone, L., Matsuda, T.D., Miyake, A., Sheikin, I., Knafo, William, Knebel, G., Howald, L., Brison, J.-P., J. Flouquet, And, Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Département de Recherche Fondamentale sur la Matière Condensée (DRFMC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: Superconductivity, Physics, Condensed matter physics, Strongly Correlated Electrons (cond-mat.str-el), Condensed Matter - Superconductivity, General Physics and Astronomy, chemistry.chemical_element, FOS: Physical sciences, Uranium, Magnetic field, [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], Superconductivity (cond-mat.supr-con), Condensed Matter - Strongly Correlated Electrons, Condensed Matter::Materials Science, Ferromagnetism, chemistry, Condensed Matter::Strongly Correlated Electrons, Cooper pair, ComputingMilieux_MISCELLANEOUS
Abstract: Recent advances on ferromagnetic superconductors, UGe2, URhGe and UCoGe are presented. The superconductivity (SC) peacefully coexists with the ferromagnetism (FM), forming the spin-triplet state of Cooper pairs. The striking new phenomena, such as SC reinforced by the magnetic field, are associated with Ising-type ferromagnetic fluctuations. A variety of ferromagnetic ordered moments between UGe2, URhGe and UCoGe affords to understand the relation between FM, tricriticality and SC., Comment: 11 pages, 16 figures, accepted for publication in J. Phys. Soc. Jpn. as a review article of Special Topics of "Recent developments in superconductivity"
Published: 2011
Full Text: View/download PDF

48. Pressure cell for transport measurements under high pressure and low temperature in pulsed magnetic fields

Author: Braithwaite, Daniel, primary, Knafo, William, additional, Settai, Rikio, additional, Aoki, Dai, additional, Kurahashi, Shuhei, additional, and Flouquet, Jacques, additional
Published: 2016
Full Text: View/download PDF

49. Thermodynamic phase diagram of Fe(Se0.5Te0.5) single crystals in fields up to 28 tesla

Author: Klein, Thierry, Braithwaite, D., Demuer, A., Knafo, William, Lapertot, G., Marcenat, C., Rodière, Pierre, Sheikin, I., Strobel, Pierre, Sulpice, André, Toulemonde, Pierre, Magnétisme et Supraconductivité (MagSup), Institut Néel (NEEL), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS), Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire national des champs magnétiques intenses - Grenoble (LNCMI-G), Université Joseph Fourier - Grenoble 1 (UJF)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Matériaux, Rayonnements, Structure (MRS), ANR-09-BLAN-0211,TETRAFER(2009), Magnétisme et Supraconductivité (NEEL - MagSup), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), and Matériaux, Rayonnements, Structure (NEEL - MRS)
Subjects: 74.25.Dw, 74.70.Xa, [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], supraconductivité
Abstract: International audience; We report on specific heat Cp , transport, Hall probe, and penetration depth measurements performed on Fe Se0.5Te0.5 single crystals Tc 14 K . The thermodynamic upper critical field Hc2 lines has been deduced from Cp measurements up to 28 T for both H c and H ab, and compared to the lines deduced from transport measurements up to 55 T in pulsed magnetic fields . We show that this thermodynamic Hc2 line presents a very strong downward curvature for T→Tc which is not visible in transport measurements. This temperature dependence associated to an upward curvature of the field dependence of the Sommerfeld coefficient confirms that Hc2 is limited by paramagnetic effects. Surprisingly this paramagnetic limit is visible here up to T/Tc 0.99 for H ab which is the consequence of a very small value of the coherence length c 0 4 Å and ab 0 15 Å , confirming the strong renormalization of the effective mass as compared to DMFT calculations previously observed in ARPES measurements A. Tamai, A. Y. Ganin, E. Rozbicki, J. Bacsa, W. Meevasana, P. D. C. King, M. Caffio, R. Schaub, S. Margadonna, K. Prassides, M. J. Rosseinsky, and F. Baumberger, Phys. Rev. Lett. 104, 097002 2010 . Hc1 measurements lead to ab 0 =430 50 nm and c 0 =1600 200 nm and the corresponding anisotropy is approximatively temperature independent 4 , being close to the anisotropy of Hc2 for T→Tc. The temperature dependence of both T2 and the electronic contribution to the specific heat confirm the nonconventional coupling mechanism in this system.
Published: 2010
Full Text: View/download PDF

50. High-field metamagnetism in the antiferromagnet CeRh$_2$Si$_2$

Author: Knafo, William, Aoki, D., Vignolles, David, Vignolle, Baptiste, Klein, Y., Jaudet, C., Villaume, A., Proust, Cyril, Flouquet, J., Laboratoire national des champs magnétiques intenses - Toulouse (LNCMI-T), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Service de Physique Statistique, Magnétisme et Supraconductivité (SPSMS - UMR 9001), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), and Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)
Subjects: [PHYS.COND.CM-S]Physics [physics]/Condensed Matter [cond-mat]/Superconductivity [cond-mat.supr-con], Condensed Matter - Strongly Correlated Electrons, Strongly Correlated Electrons (cond-mat.str-el), FOS: Physical sciences, ComputingMilieux_MISCELLANEOUS
Abstract: A study of the antiferromagnet CeRh$_2$Si$_2$ by torque, magnetostriction, and transport in pulsed magnetic fields up to 50 Tesla and by thermal expansion in static fields up to 13 Tesla is presented. The magnetic field-temperature phase diagram of CeRh$_2$Si$_2$, where the magnetic field is applied along the easy axis $\mathbf{c}$, is deduced from these measurements. The second-order phase transition temperature $T_{N}$ and the first-order phase transition temperature $T_{1,2}$ (=~36 K and 26 K at zero-field, respectively) decrease with increasing field. The field-induced antiferromagnetic-to-paramagnetic borderline $H_c$, which equals 26 T at 1.5 K, goes from first-order at low temperature to second-order at high temperature. The magnetic field-temperature phase diagram is found to be composed of (at least) three different antiferromagnetic phases. These are separated by the first-order lines $H_{1,2}$, corresponding to $T_{1,2}$ at H=0, and $H_{2,3}$, which equals 25.5 T at 1.5 K. A maximum of the $T^2$-coefficient $A$ of the resistivity is observed at the onset of the high-field polarized regime, which is interpreted as the signature of an enhanced effective mass at the field-induced quantum instability. The magnetic field dependence of the $A$ coefficient in CeRh$_2$Si$_2$ is compared with its pressure dependence, and also with the field dependence of $A$ in the prototypal heavy-fermion system CeRu$_2$Si$_2$., 10 pages, 11 figures
Published: 2010
Full Text: View/download PDF

Catalog

Books, media, physical & digital resources

See catalog results

Searchworks

Select search scope, currently: Articles Catalog books, media & more in Jio Institute collections Articles journal articles & other e-resources

Search

Search Constraints

Refine your results

Search Limiters

Topic

Publication Year Range

Language

Publication Type

Journal

Database

Publisher

96 results on '"Knafo, William"'

Search Results

Catalog

Select search scope, currently: Articles

Catalog

books, media & more in Jio Institute collections

Articles

journal articles & other e-resources