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38 results on '"Coldea, A.I."'

1. Multiband description of the upper critical field of bulk FeSe

Author

Bristow, M., Gower, A., Prentice, J.C.A., Watson, M.D., Zajicek, Z., Blundell, S.J., Haghighirad, A.A., McCollam, A., Coldea, A.I., Bristow, M., Gower, A., Prentice, J.C.A., Watson, M.D., Zajicek, Z., Blundell, S.J., Haghighirad, A.A., McCollam, A., and Coldea, A.I.

Abstract

Item does not contain fulltext

Published
2023

3. Unconventional localization of electrons inside of a nematic electronic phase

Author

Farrar, Liam S., Zajicek, Z., Morfoot, A.B., Bristow, M., Humphries, O.S., Haghighirad, A.A., McCollam, A., Bending, Simon J., Coldea, A.I., Farrar, Liam S., Zajicek, Z., Morfoot, A.B., Bristow, M., Humphries, O.S., Haghighirad, A.A., McCollam, A., Bending, Simon J., and Coldea, A.I.

Abstract

Contains fulltext : 285848.pdf (Publisher’s version ) (Open Access)

Published
2022

7. Anomalous high-magnetic field electronic state of the nematic superconductors FeSe1 - xSx

Author

Bristow, M., Reiss, P., Haghighirad, A.A., Zajicek, Z., Singh, S.J., Wolf, T., Graf, D., Knafo, W., McCollam, A., Coldea, A.I., Bristow, M., Reiss, P., Haghighirad, A.A., Zajicek, Z., Singh, S.J., Wolf, T., Graf, D., Knafo, W., McCollam, A., and Coldea, A.I.

Abstract

Contains fulltext : 228093.pdf (publisher's version ) (Open Access)

Published
2020

13. 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

14. Multi-band magnetotransport in exfoliated thin films of Cu x Bi2Se3

Author

Alexander-Webber, J. A., Huang, J., Beilsten-Edmands, J, Čermák, Patrik, Drašar, Čestmír, Nicholas, R.J., Coldea, A.I., Alexander-Webber, J. A., Huang, J., Beilsten-Edmands, J, Čermák, Patrik, Drašar, Čestmír, Nicholas, R.J., and Coldea, A.I.

Abstract

We report magnetotransport studies in thin (<100 nm) exfoliated films of Cu x Bi2Se3 and we detect an unusual electronic transition at low temperatures. Bulk crystals show weak superconductivity with K and a possible electronic phase transition around 200 K. Following exfoliation, superconductivity is supressed and a strongly temperature dependent multi-band conductivity is observed for T < 30 K. This transition between competing conducting channels may be enhanced due to the presence of electronic ordering, and could be affected by the presence of an effective internal stress due to Cu intercalation. By fitting to the weak antilocalisation conductivity correction at low magnetic fields we confirm that the low temperature regime maintains a quantum phase coherence length nm indicating the presence of topologically protected surface states., Pojednáváme o magnetotransportních studiích na tenkých (<100 nm) exfoliovaných vrstvách CuxBi2Se3 a zjišťujeme neobvyklý elektronický přechod při nízkých teplotách. Objemové krystaly vykazují slabou supravodivost s Tc ~ 3,5 K a možný elektronický fázový přechod okolo 200 K. Po exfoliaci je supravodivost potlačena a silně teplotně závislá více-pásová vodivost je pozorována při T < 30 K. Tento přechod mezi konkurenčními vodivostními kanály může být zvýšen kvůli přítomnosti elektronického uspořádání a může být ovlivněn přítomností účinného vnitřního pnutí kvůli interkalaci Cu. Fitováním korekce na slabou nelokalizovanou vodivost při nízkých magnetických polích potvrzujeme, že nízkoteplotní režim udržuje kvantovou fázovou koherenční délku L>100 nm, což indikuje přítomnost topologicky chráněných povrchových stavů.

Published
2019

16. Evolution of the Fermi surface of BaFe2(As1-xPx){2} on entering the superconducting dome

Author

Shishido, H., Bangura, A.F., Coldea, A.I., Tonegawa, S., Hashimoto, K., Kasahara, S., Rourke, P.M.C., Ikeda, H., Terashima, T., Settai, R., Onuki, Y., Vignolles, D., Proust, C., Vignolle, B., MC Collam, A., Matsuda, Y., Shibauchi, T., Carrington, A., Department of Physics, Kyoto University, Kyoto University [Kyoto], Research Center for Low Temperature and Materials Sciences, 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), Department of Physics, Kyoto University (DEPARTMENT OF PHYSICS, KYOTO UNIVERSITY), Division of New Material Science, Institute for Solid State Physics (ISSP), Institute for Solid State Physics [Tokyo] (ISSP), The University of Tokyo (UTokyo)-The University of Tokyo (UTokyo), Kyoto University, 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), 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::Superconductivity, Condensed Matter::Strongly Correlated Electrons, Correlated Electron Systems / High Field Magnet Laboratory (HFML), GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), ComputingMilieux_MISCELLANEOUS
Abstract

Using the de Haas-van Alphen effect we have measured the evolution of the Fermi surface of BaFe2(As1-xPx){2} as a function of isoelectric substitution (As/P) for 0.41

Published
2016

17. Anisotropic fluctuations and quasiparticle excitations in FeSe_0.5Te_0.5

Author

Serafin, A., Coldea, A.I., Ganin, A.Y., Rosseinsky, M.J., Prassides, K., Vignolles, David, Carrington, A., 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), 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), 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], Superconductivity (cond-mat.supr-con), Condensed Matter - Superconductivity, FOS: Physical sciences, ComputingMilieux_MISCELLANEOUS
Abstract

We present data for the temperature dependence of the magnetic penetration depth lambda(T), heat capacity C(T), resistivity R(T) and magnetic torque ?tau for highly homogeneous single crystal samples of Fe1:0Se0:44(4)Te0:56(4). lambda(T) was measured down to 200mK in zero field. We find lambda(T) follows a power law lambda~T^n with n = 2.2 +/- 0.1. This is similar to some 122 iron-arsenides and likely results from a sign-changing pairing state combined with strong scattering. Magnetic fields of up to B =55T or 14T were used for the ? tau(B) and C(T)/R(T) measurements respectively. The specific heat, resistivity and torque measurements were used to map out the (H,T) phase diagram in this material. All three measurements were conducted on exactly the same single crystal sample so that the different information revealed by these probes is clearly distinguished. Heat capacity data strongly resemble those found for the high Tc cuprates, where strong fluctuation effects wipe-out the phase transition at Hc2. Unusually, here we find the fluctuation effects appear to be strongly anisotropic., 10 pages, 9 figures, submitted to PRB

Published
2016
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18. Fermi surface of SrFe2P2 determined by the de Haas- van Alphen effect

Author

Analytis, J.G., Andrew, C.M.J., Coldea, A.I., MC Collam, A., Chu, J.-H., McDonald, R.D., Fisher, I.R., and Carrington, A.

Subjects
Correlated Electron Systems / High Field Magnet Laboratory (HFML), GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries)
Abstract

Contains fulltext : 145259.pdf (Publisher’s version ) (Open Access) 5 p.

Published
2009

19. Dichotomy between the Hole and Electron Behavior in Multiband Superconductor FeSe Probed by Ultrahigh Magnetic Fields

Author

Watson, M.D., Yamashita, T., Kasahara, S., Knafo, W., Nardone, M., Beard, J., Hardy, F., McCollam, A., Narayanan, A., Blake, S.F., Wolf, T., Haghighirad, A.A., Meingast, C., Schofield, A.J., Lohneysen, H. von, Matsuda, Y., Coldea, A.I., Shibauchi, T., Watson, M.D., Yamashita, T., Kasahara, S., Knafo, W., Nardone, M., Beard, J., Hardy, F., McCollam, A., Narayanan, A., Blake, S.F., Wolf, T., Haghighirad, A.A., Meingast, C., Schofield, A.J., Lohneysen, H. von, Matsuda, Y., Coldea, A.I., and Shibauchi, T.

Abstract

Contains fulltext : 149434.pdf (publisher's version ) (Open Access)

Published
2015

20. Fermi surface of IrTe2 in the valence-bond state as determined by quantum oscillations

Author

Blake, S.F., Watson, M.D., McCollam, A., Kasahara, S., Johnson, R.D., Narayanan, A., Pascut, G.L., Haule, K., Kiryukhin, V., Yamashita, T., Watanabe, D., Shibauchi, T., Matsuda, Y., Coldea, A.I., Blake, S.F., Watson, M.D., McCollam, A., Kasahara, S., Johnson, R.D., Narayanan, A., Pascut, G.L., Haule, K., Kiryukhin, V., Yamashita, T., Watanabe, D., Shibauchi, T., Matsuda, Y., and Coldea, A.I.

Abstract

Contains fulltext : 149442.pdf (publisher's version ) (Open Access)

Published
2015

21. Emergence of the nematic electronic state in FeSe

Author

Watson, M.D., Kim, T.K., Haghighirad, A.A., Davies, N.R., McCollam, A., Narayanan, A., Blake, S.F., Chen, Y.L., Ghannadzadeh, S., Schofield, A.J., Hoesch, M., Meingast, C., Wolf, T., Coldea, A.I., Watson, M.D., Kim, T.K., Haghighirad, A.A., Davies, N.R., McCollam, A., Narayanan, A., Blake, S.F., Chen, Y.L., Ghannadzadeh, S., Schofield, A.J., Hoesch, M., Meingast, C., Wolf, T., and Coldea, A.I.

Abstract

Contains fulltext : 149439.pdf (publisher's version ) (Open Access)

Published
2015

22. Cascade of field-induced magnetic transitions in a frustrated antiferromagnetic metal

Author

Coldea, A.I., Seabra, L., McCollam, A., Carrington, A., Malone, L., Bangura, A.F., Vignolles, D., Rhee, P.G. van, McDonald, R.D., Sörgel, T., Jansen, M, Shannon, N., Coldea, R., Coldea, A.I., Seabra, L., McCollam, A., Carrington, A., Malone, L., Bangura, A.F., Vignolles, D., Rhee, P.G. van, McDonald, R.D., Sörgel, T., Jansen, M, Shannon, N., and Coldea, R.

Abstract

Contains fulltext : 133179.pdf (publisher's version ) (Open Access)

Published
2014

23. Field-induced magnetic transitions in Ca 10 (Pt 3 As 8 )((Fe 1−x Pt x ) 2 As 2 ) 5 compounds

Author

Watson, M.D., McCollam, A., Blake, S.F., Vignolles, D., Drigo, L., Mazin, I.I., Guterding, D., Jeschke, H.O., Valentí, R., Ni, N., Cava, R., Coldea, A.I., Watson, M.D., McCollam, A., Blake, S.F., Vignolles, D., Drigo, L., Mazin, I.I., Guterding, D., Jeschke, H.O., Valentí, R., Ni, N., Cava, R., and Coldea, A.I.

Abstract

Contains fulltext : 133194.pdf (publisher's version ) (Open Access)

Published
2014

24. De haas-van alphen study of the fermi surfaces of superconducting lifep and lifeas

Author

Putzke, C., Coldea, A.I., Guillamon, I., Vignolles, D., MC Collam, A., LeBoeuf, D., Watson, M.D., Mazin, I.I., Kasahara, S., Terashima, T., Shibauchi, T., Matsuda, Y., Carrington, A., Putzke, C., Coldea, A.I., Guillamon, I., Vignolles, D., MC Collam, A., LeBoeuf, D., Watson, M.D., Mazin, I.I., Kasahara, S., Terashima, T., Shibauchi, T., Matsuda, Y., and Carrington, A.

Abstract

Contains fulltext : 93802.pdf (publisher's version ) (Open Access)

Published
2012

25. Evolution of the fermi surface of BaFe2(As1-xPx)2 on entering the superconducting dome

Author

Shishido, H., Bangura, A.F., Coldea, A.I., Tonegawa, S., Hashimoto, K., Kasahara, S., Rourke, P.M.C., Ikeda, H., Terashima, T., Settai, R., Onuki, Y., Vignolles, D., Proust, C., Vignolle, B., MC Collam, A., Matsuda, Y., Shibauchi, T., Carrington, A., Shishido, H., Bangura, A.F., Coldea, A.I., Tonegawa, S., Hashimoto, K., Kasahara, S., Rourke, P.M.C., Ikeda, H., Terashima, T., Settai, R., Onuki, Y., Vignolles, D., Proust, C., Vignolle, B., MC Collam, A., Matsuda, Y., Shibauchi, T., and Carrington, A.

Abstract

Contains fulltext : 83661.pdf (publisher's version ) (Open Access)

Published
2010

32. Growth of large La1-xSrxMnO3 single crystals under argon pressure by the floating-zone technique

Author

Prabhakaran, D., Coldea, A.I., Boothroyd, A.T., and Blundell, S.J.

Subjects
*CRYSTAL growth, *TWINNING (Crystallography), *CRYSTALLOGRAPHY, *OXIDE minerals
Abstract

We report the growth of single crystals of La1-xSrxMnO3 (x=0.0–0.3) by the floating-zone technique in an image furnace under high argon pressure (6–8 atm). An excess of Mn in the polycrystalline starting material was used to compensate for the evaporation during growth. Single crystals of diameter 8 mm and length 70 mm have been obtained. The phase purity, composition and quality of the crystals were analysed by X-ray diffraction and electron probe microanalysis. We discuss the effect on the crystal growth of varying the amount of Mn excess and of the composition of the growth atmosphere. We also present magnetization and resistivity data for a few of the samples. [Copyright &y& Elsevier]

Published
2002
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33. The role of magnetic ions on the magnetotransport properties of the charge-transfer salts <f>β″</f>-BEDT-<f>TTF4[(H3O)M(C2O4)3]C5H5N</f> where <f>M=Ga3+</f>, <f>Cr3+</f> or <f>Fe3+</f>

Author

Coldea, A.I., Bangura, A.F., Singleton, J., Ardavan, A., Akutsu-Sato, A., Akutsu, H., S. Turner, S., and Day, P.

Subjects
*MAGNETIC ions, *CHARGE transfer, *FERMI surfaces, *SUPERCONDUCTIVITY
Abstract

We report high-field magnetotransport measurements on β″-BEDT-TTF4[(H3O)M(C2O4)3]C5H5N, where M=Ga3+, Cr3+ or Fe3+. In spite of the differing M ions, these compounds have very similar Fermi surfaces. We observe four distinct Shubnikov–de Haas frequencies, corresponding to four Fermi-surface pockets; the frequencies exhibit the additive relationship expected for a compensated semimetal. The compounds show paramagnetic behaviour and no superconductivity down to 0.5 K, in contrast to other materials of the same family with different solvent molecules. [Copyright &y& Elsevier]

Published
2004
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36. Strain tuning of nematicity and superconductivity in single crystals of FeSe

Author

Amalia I. Coldea, Matthew Bristow, Michele Ghini, Amir A. Haghighirad, Samuel Sutherland, Joseph C. A. Prentice, S. Sanna, Ghini M., Bristow M., Prentice J.C.A., Sutherland S., Sanna S., Haghighirad A.A., and Coldea A.I.

Subjects
Phase transition, Materials science, unconventional superconductivity, Lattice (group), FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Superconductivity (cond-mat.supr-con), Condensed Matter - Strongly Correlated Electrons, uniaxial strain, Condensed Matter::Materials Science, Electrical resistivity and conductivity, Hall effect, Condensed Matter::Superconductivity, 0103 physical sciences, 010306 general physics, Superconductivity, Condensed Matter - Materials Science, Strongly Correlated Electrons (cond-mat.str-el), Condensed matter physics, Strain (chemistry), Condensed Matter - Superconductivity, Materials Science (cond-mat.mtrl-sci), 021001 nanoscience & nanotechnology, 0210 nano-technology, magnetotransport, Single crystal, Critical exponent, electric resistivity
Abstract

Strain is a powerful experimental tool to explore new electronic states and understand unconventional superconductivity. Here, we investigate the effect of uniaxial strain on the nematic and superconducting phase of single crystal FeSe using magnetotransport measurements. We find that the resistivity response to the strain is strongly temperature dependent and it correlates with the sign change in the Hall coefficient being driven by scattering, coupling with the lattice and multiband phenomena. Band structure calculations suggest that under strain the electron pockets develop a large in-plane anisotropy as compared with the hole pocket. Magnetotransport studies at low temperatures indicate that the mobility of the dominant carriers increases with tensile strain. Close to the critical temperature, all resistivity curves at constant strain cross in a single point, indicating a universal critical exponent linked to a strain-induced phase transition. Our results indicate that the superconducting state is enhanced under compressive strain and suppressed under tensile strain, in agreement with the trends observed in FeSe thin films and overdoped pnictides, whereas the nematic phase seems to be affected in the opposite way by the uniaxial strain. By comparing the enhanced superconductivity under strain of different systems, our results suggest that strain on its own cannot account for the enhanced high $T_c$ superconductivity of FeSe systems., Comment: 11 pages, 8 figures

Published
2021
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37. Millimetre-wave studies on the high-spin molecules Cr10(OMe)20(O2CCMe3)10 and Cr12O9(OH)3(O2CCMe3)15

Author

Sharmin, S., Ardavan, A., Blundell, S.J., and Coldea, A.I.

Subjects
*ELECTRON paramagnetic resonance, *PARTICLES (Nuclear physics), *SPECTRUM analysis, *TEMPERATURE
Abstract

Abstract: We report millimetre-wave electron spin resonance (ESR) measurements on single crystals of the high-spin molecules Cr10(OMe)20(O2CCMe3)10 and Cr12O9(OH)3(O2CCMe3)15 within a temperature range of 1.4K to 50K and in magnetic fields of up to 5 Tesla. In our experiments it is possible to vary the orientation of the magnetic field with respect to the crystal axes, and thus to study the ESR lineshapes as a function of both temperature and angle. Our results confirm that Cr10(OMe)20(O2CCMe3)10 behaves as a single-molecule magnet with S= 15 and D= -0.03K, while Cr12O9(OH)3(O2CCMe3)15 has S =6 and D ∼0.1K. A comparison of the experimental spectra with numerical simulations gives good agreement at low temperatures. At higher temperatures, we observe a narrowing of the ESR spectrum that is not explained by simple models. [Copyright &y& Elsevier]

Published
2005
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38. Angle-dependent magneto-transport measurements on κ- (BEDT-TTF)2Cu(NCS)2 under pressure

Author

Bangura, A.F., Goddard, P.A., Tozer, S., Coldea, A.I., McDonald, R.D., Singleton, J., Ardavan, A., and Schleuter, J.

Subjects
*SUPERCONDUCTORS, *MAGNETIC fields, *OSCILLATIONS, *ELECTRONS
Abstract

Abstract: Magnetotransport measurements have been performed on single crystals of κ-(BEDT-TTF) 2 CuNCS) 2 in fields of up to 33 T at temperatures between 500mK and 4.2K. Using a diamond anvil cell mounted on a goniometer, measurements of the angle and temperature dependence of the interlayer resistance, R ZZ under hydrostatic pressures between 1.1kbar and 17.3kbar were performed. For the first time we have been able to measure angle-dependent magnetoresistance oscillations under pressure due to both the ID and 2D Fermi surfaces in addition to Shubnikov de Haas oscillations. The results show that the shape of the elliptical quasi-2D Fermi-pocket is more elongated under a hydrostatic pressure of 9.8kbar compared with ambient pressure. When the magnetic field B is close to parallel to the highly conductive plane, bc, a peak in R ZZ is observed with an angular width determined by the ratio of the maximum inter- and intra-layer Fermi velocities. The width of this peak is found to increase with pressure suggesting that the Fermi surface becomes more three-dimensional upon application of pressure. [Copyright &y& Elsevier]

Published
2005
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