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2. Polarized Neutron on URu2Si2

Author

Bourdarot, F., Ressouche, E., Ballou, R., Raymond, S., Aoki, D., Martin, N., Regnault, L.-P., Simonet, V., Fernandez-Diaz, M.T., Stunault, A., Taufour, V., and Flouquet, J.

Published
2013
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8. Terahertz Magneto-optical investigation of quadrupolar spin-lattice effects in magnetically frustrated Tb 2 Ti 2 O 7

Author

Amelin, K., Alexanian, Y., Nagel, U., Rõõm, T., Robert, J., Debray, J., Simonet, V., Decorse, C., Wang, Z., Ballou, R., Constable, E., De Brion, Sophie, National Institute of Chemical Physics and Biophysics = Keemilise ja bioloogilise füüsika instituut [Estonie] (NICPB | KBFI), Magnétisme et Supraconductivité (MagSup), Institut Néel (NEEL), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Cristaux Massifs (CrisMass), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institute of Radiation Physics [Dresden], Helmholtz-Zentrum Dresden-Rossendorf (HZDR), and Vienna University of Technology (TU Wien)

Subjects
pyrochlore, frustration, THz spectroscopy, spin-lattice coupling, [PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2020

9. Fragmented monopole crystal, dimer entropy and Coulomb interactions in Dy 2 Ir 2 O 7

Author

Cathelin, V., Lefrançois, E., Robert, J., Guruciaga, P., Paulsen, C., Prabhakaran, D., Lejay, P., Damay, F., Ollivier, J., Fåk, B., Chapon, L., Ballou, R., Simonet, V., Holdsworth, P., Lhotel, E., Magnétisme et Supraconductivité (MagSup), Institut Néel (NEEL), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Institut Laue-Langevin (ILL), ILL, Consejo Nacional de Investigaciones Científicas y Técnicas [Buenos Aires] (CONICET), Clarendon Laboratory [Oxford], University of Oxford [Oxford], Cristaux Massifs (CrisMass), Groupe Diffraction Poudres (GDP), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, DIAMOND Light source, Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure - Lyon (ENS Lyon)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, Magnétisme et Supraconductivité (NEEL - MagSup), University of Oxford, Croissance Cristalline et MicroAnalyse (NEEL - C2MA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2020

10. High-order crystal field and rare-earth magnetism in RECo5 intermetallics

Author

Pourovskii, L. V., Boust, J., Ballou, R., Eslava, G. Gomez, and Givord, D.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons, Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences
Abstract

Crystal-field (CF) effects on the rare-earth (RE) ions in ferrimagnetic intermetallics NdCo$_5$ and TbCo$_5$ are evaluated using an ab initio density functional + dynamical mean-field theory approach in conjunction with a quasi-atomic approximation for on-site electronic correlations on the localized 4$f$ shell. The study reveals an important role of the high-order sectoral harmonic component of the CF in the magnetism of RECo$_5$ intermetallics. An unexpectedly large value is computed in the both systems for the corresponding crystal-field parameter (CFP) $A_6^6 \langle r^6 \rangle$, far beyond what one would expect from only electrostatic contributions. It allows solving the enigma of the non-saturation of zero-temperature Nd magnetic moments in NdCo$_5$ along its easy axis in the Co exchange field. This unsaturated state had been previously found out from magnetization distribution probed by polarised neutron elastic scattering but had so far remained theoretically unexplained. The easy plane magnetic anisotropy of Nd in NdCo$_5$ is strongly enhanced by the large value of $A_6^6\langle r^6 \rangle$. Counter-intuitively, the polar dependence of anisotropy energy within the easy plane remains rather small. The easy plane magnetic anisotropy of Nd is reinforced up to high temperatures, which is explained through $J$-mixing effects. The calculated ab initio anisotropy constants of NdCo$_5$ and their temperature dependence are in quantitative agreement with experiment. Unlike NdCo$_5$, the $A_6^6 \langle r^6 \rangle$ CFP has negligible effects on the Tb magnetism in TbCo$_5$ suggesting that its impact on the RE magnetism is ion-specific across the RECo$_5$ series. The origin of its large value is the hybridization of RE and Co states in a hexagonally coordinated local environment of the RE ion in RECo$_5$ intermetallics., 17 pages, 10 figures

Published
2020

15. Does (TaSe4)2I really harbor an axionic charge density wave?

Author

Sinchenko, A. A., Ballou, R., Lorenzo, J. E., Grenet, Th., and Monceau, P.

Subjects
*CHARGE density waves, *WEYL fermions, *POLARONS, *MAGNETIC fields, *ELECTRIC fields, *HIGH temperatures
Abstract

A recent experimental work has reported an excess of the non-linear conductivity in the charge density wave (CDW) sliding mode of the quasi one-dimensional compound (TaSe4)2I, when a magnetic field is applied co-linearly to the electric field [Gooth et al., Nature 575, 315 (2019)]. This result has opened a conceptual approach, where the CDW gap in (TaSe4)2I is opened between Weyl fermions of opposite chirality with the assumption that this compound is a Weyl semi-metal in its undistorted high temperature phase. We report measurements in the sliding state of (TaSe4)2I performed in similar conditions. We have found no increase in the magnetoconductivity. In our attempts for understanding this unsettling discrepancy, we stress the specific nature of the Peierls transition in (TaSe4)2I and the strong electron-phonon coupling present in this compound. Given the lack of further evidence, we think that it is premature to assert that (TaSe4)2I is an axionic insulator. [ABSTRACT FROM AUTHOR]

Published
2022
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16. Dimer Physics in the Frustrated Cairo Pentagonal Antiferromagnet Bi2Fe4O9

Author

Beauvois, K., Simonet, V., Petit, S., Robert, J., Bourdarot, F., Gospodinov, M., Mukhin, A. a., Ballou, R., Skumryev, V., Ressouche, E., Magnétisme et Supraconductivité (MagSup), Institut Néel (NEEL), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Institut Laue-Langevin (ILL), ILL, 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 (UGA)-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 (UGA), LLB - Nouvelles frontières dans les matériaux quantiques (NFMQ), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, Bulgarian Academy of Sciences (BAS), A. M. Prokhorov General Physics Institute (GPI), Russian Academy of Sciences [Moscow] (RAS), Institució Catalana de Recerca i Estudis Avançats (ICREA), Magnétisme et Supraconductivité (NEEL - MagSup), CEA- Saclay (CEA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
Inorganic Chemistry, Condensed Matter - Strongly Correlated Electrons, Strongly Correlated Electrons (cond-mat.str-el), Structural Biology, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], FOS: Physical sciences, General Materials Science, Condensed Matter::Strongly Correlated Electrons, Physical and Theoretical Chemistry, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Condensed Matter Physics, Biochemistry
Abstract

The research field of magnetic frustration is dominated by triangle-based lattices but exotic phenomena can also be observed in pentagonal networks. A peculiar noncollinear magnetic order is indeed known to be stabilized in Bi2Fe4O9 materializing a Cairo pentagonal lattice. We present the spin wave excitations in the magnetically ordered state, obtained by inelastic neutron scattering. They reveal an unconventional excited state related to local precession of pairs of spins. The magnetic excitations are then modeled to determine the superexchange interactions for which the frustration is indeed at the origin of the spin arrangement. This analysis unveils a hierarchy in the interactions, leading to a paramagnetic state (close to the N\'eel temperature) constituted of strongly coupled dimers separated by much less correlated spins. This produces two types of response to an applied magnetic field associated with the two nonequivalent Fe sites, as observed in the magnetization distributions obtained using polarized neutrons., Comment: Article: 6 pages, 3 figures. Supplemental Material: 10 pages, 10 figures

Published
2019

17. Spin decoupling under a staggered field in the Gd 2 Ir 2 O 7 pyrochlore

Author

Lefrançois, E., Mangin-Thro, L., Lhotel, Elsa, Robert, J., Petit, S., Cathelin, V., Fischer, E., Colin, Claire, Damay, F., Ollivier, J., Lejay, P., Chapon, L., Simonet, V., Ballou, R., Magnétisme et Supraconductivité (MagSup ), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut Laue-Langevin (ILL), ILL, Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, Matériaux, Rayonnements, Structure (MRS), Cristaux Massifs (CrisMass), DIAMOND Light source, Magnétisme et Supraconductivité (NEEL - MagSup), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Matériaux, Rayonnements, Structure (NEEL - MRS), and Croissance Cristalline et MicroAnalyse (NEEL - C2MA)

Subjects
Condensed Matter::Strongly Correlated Electrons, [PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el]
Abstract

International audience; The influence of a staggered molecular field in frustrated rare-earth pyrochlores, produced via the magnetic iridium occupying the transition metal site, can generate exotic ground states, such as the fragmentation of the magnetization in the Ho compound. At variance with the Ising Ho3+ moment, we focus on the behavior of the quasi-isotropic magnetic moment of the Gd3+ ion at the rare-earth site. By means of macroscopic measurements and neutron scattering, we find a complex situation where different components of the magnetic moment are decoupled and contribute to two antiferromagnetic noncollinear arrangements: a high-temperature all in–all out order induced by the Ir molecular field, and Palmer and Chalker correlations that tend to order at much lower temperatures. This is enabled by the anisotropic nature of the Gd-Gd interactions and requires a weak easy-plane anisotropy of the Gd3+ moment due to the mixing of the ground state with multiplets of higher spectral terms.

Published
2019

22. Fragmented monopole crystal, dimer entropy, and Coulomb interactions in Dy2Ir2O7

Author

Cathelin, V., Lefran��ois, E., Robert, J., Guruciaga, P. C., Paulsen, C., Prabhakaran, 1 D., Lejay, P., Damay, F., Ollivier, J., F��k, B., Chapon, L. C., Ballou, R., Simonet, V., Holdsworth, P. C. W., and Lhotel, E.

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Materials Science, Strongly Correlated Electrons (cond-mat.str-el), Condensed Matter::Superconductivity, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences
Abstract

Neutron scattering, specific heat and magnetisation measurements on both powders and single crystals reveal that Dy$_2$Ir$_2$O$_7$ realizes the fragmented monopole crystal state in which antiferromagnetic order and a Coulomb phase spin liquid co-inhabit. The measured residual entropy is that of a hard core dimer liquid, as predicted. Inclusion of Coulomb interactions allows for a quantitative description of both the thermodynamic data and the magnetisation dynamics, with the energy scale given by deconfined defects in the emergent ionic crystal. Our data reveal low energy excitations, as well as a large distribution of energy barriers down to low temperatures, while the magnetic response to an applied field suggests that domain wall pinning is important; results that call for further theoretical modelling., 6 pages + supp. mat. 6 pages

Published
2020

23. Crystallography: Symmetry groups and group representations

Author

Grenier B. and Ballou R.

Subjects
Physics, QC1-999
Abstract

This lecture is aimed at giving a sufficient background on crystallography, as a reminder to ease the reading of the forthcoming chapters. It more precisely recalls the crystallographic restrictions on the space isometries, enumerates the point groups and the crystal lattices consistent with these, examines the structure of the space group, which gathers all the spatial invariances of a crystal, and describes a few dual notions. It next attempts to familiarize us with the representation analysis of physical states and excitations of crystals.

Published
2012
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24. An introduction to the linear representations of finite groups

Author

Ballou R.

Subjects
Physics, QC1-999
Abstract

A few elements of the formalism of finite group representations are recalled. As to avoid a too mathematically oriented approach the discussed items are limited to the most essential aspects of the linear and matrix representations of standard use in chemistry and physics.

Published
2012
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25. CXCR3+ T Follicular Helper Cells Induced by Co-Administration of RTS,S/AS01B and Viral-Vectored Vaccines Are Associated With Reduced Immunogenicity and Efficacy Against Malaria

Author

Ewer (nee Russell), K, Bowyer, G, Grobbelaar, A, Rampling, T, Venkatraman, N, Morelle, D, Ballou, R, and Hill, A

Subjects
lcsh:Immunologic diseases. Allergy, CXCR3, vaccine, antibody, Immunology, efficacy, malaria, lcsh:RC581-607, T follicular helper cell, RTSS viral-vectored vaccines, Original Research
Abstract

A malaria vaccine strategy targeting multiple lifecycle stages may be required to achieve a high level of efficacy. In two Phase IIa clinical trials, we tested immunogenicity and efficacy of RTS,S/AS01B administered alone, in a staggered regimen with viral-vectored vaccines or co-administered with viral-vectored vaccines. RTS,S/AS01B induces high titers of antibody against sporozoites and viral-vectored vaccines ChAd63 ME-TRAP and MVA ME-TRAP induce potent T cell responses against infected hepatocytes. By combining these two strategies, we aimed to improve efficacy by inducing immune responses targeting multiple parasite antigens. Vaccination with RTS,S/AS01B alone or in a staggered regimen with viral vectors produced strong immune responses and demonstrated high levels of protection against controlled human malaria infection. However, concomitant administration of these vaccines significantly reduced humoral immunogenicity and protective efficacy. Strong Th1-biased cytokine responses induced by MVA ME-TRAP were associated with a skew in circulating T follicular helper cells toward a CXCR3+ phenotype and a reduction in antibody quantity and quality. This study illustrates that while a multistage-targeting vaccine strategy could provide high-level efficacy, the regimen design will require careful optimization.

Published
2018

29. Experimental evidence of symmetry breaking in the multiferroic Ba 3 NbFe 3 Si 2 O 14 using sound velocity measurements

Author

Quirion, G., Bidaud, C., Quilliam, J. A., Lejay, P., Simonet, V., Ballou, R., Institut de biologie et chimie des protéines [Lyon] (IBCP), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Cristaux Massifs (CrisMass), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), and Magnétisme et Supraconductivité (MagSup )

Subjects
[PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2017

30. Crystal symmetry lowering in chiral multiferroic ${\mathrm{Ba}}_{3}{\mathrm{TaFe}}_{3}{\mathrm{Si}}_{2}{\mathrm{O}}_{14}$ observed by x-ray magnetic scattering

Author

Ramakrishnan, M., Joly, Y., Windsor, Y. W., Rettig, L., Alberca, Aurora, Bothschafter, E. M., Lejay, P., Ballou, R., Simonet, V., Scagnoli, V., and Staub, U.

Abstract

Chiral multiferroic langasites have attracted attention due to their doubly chiral magnetic ground state within an enantiomorphic crystal. We report on a detailed resonant soft x-ray diffraction study of the multiferroic Ba3TaFe3Si2O14 at the Fe L2,3 and oxygen K edges. Below TN (≈27K) we observe the satellite reflections (0,0,τ), (0,0,2τ), (0,0,3τ), and (0,0,1−3τ) where τ≈0.140±0.001. The dependence of the scattering intensity on x-ray polarization and azimuthal angle indicate that the odd harmonics are dominated by the out-of-plane (ˆc axis) magnetic dipole while the (0,0,2τ) originates from the electron density distortions accompanying magnetic order. We observe dissimilar energy dependencies of the diffraction intensity of the purely magnetic odd-harmonic satellites at the Fe L3 edge. Utilizing first-principles calculations, we show that this is a consequence of the loss of threefold crystal symmetry in the multiferroic phase.

Published
2017

31. Crystal symmetry lowering in chiral multiferroic Ba 3 TaFe 3 Si 2 O 14 observed by x-ray magnetic scattering

Author

Ramakrishnan, M., Joly, Yves, Windsor, Y. W., Rettig, L., Alberca, A., Bothschafter, E. M., Lejay, P., Ballou, R., Simonet, V., Scagnoli, V., Staub, U., The Swiss Light Source (SLS) (SLS-PSI), Paul Scherrer Institute (PSI), Surfaces, Interfaces et Nanostructures (SIN ), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Cristaux Massifs (CrisMass), and Magnétisme et Supraconductivité (MagSup )

Subjects
X-ray magnetic scattering, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], multiferroic
Abstract

International audience; Chiral multiferroic langasites have attracted attention due to their doubly chiral magnetic ground state withinan enantiomorphic crystal. We report on a detailed resonant soft x-ray diffraction study of the multiferroicBa3TaFe3Si2O14 at the FeL2,3 and oxygenK edges. BelowTN (≈27K)we observe the satellite reflections (0,0,τ ),(0,0,2τ ), (0,0,3τ ), and (0,0,1 − 3τ) where τ ≈ 0.140 ± 0.001. The dependence of the scattering intensity onx-ray polarization and azimuthal angle indicate that the odd harmonics are dominated by the out-of-plane (ˆcaxis) magnetic dipole while the (0,0,2τ ) originates from the electron density distortions accompanying magneticorder.We observe dissimilar energy dependencies of the diffraction intensity of the purelymagnetic odd-harmonicsatellites at the Fe L3 edge. Utilizing first-principles calculations, we show that this is a consequence of the lossof threefold crystal symmetry in the multiferroic phase.

Published
2017

32. Magnetic charge injection in spin ice: a new way to fragmentation

Author

Lefran��ois, E., Cathelin, V., Lhotel, E., Robert, J., Lejay, P., Colin, C. V., Canals, B., Damay, F., Ollivier, J., F��k, B., Chapon, L. C., Ballou, R., and Simonet, V.

Subjects
Condensed Matter - Strongly Correlated Electrons, Strongly Correlated Electrons (cond-mat.str-el), FOS: Physical sciences, Condensed Matter::Strongly Correlated Electrons
Abstract

The complexity embedded in condensed matter fertilizes the discovery of new states of matter, enriched by ingredients like frustration. Illustrating examples in magnetic systems are Kitaev spin liquids, skyrmions phases, or spin ices. These unconventional ground states support exotic excitations, for example the magnetic charges in spin ices, also called monopoles. Beyond their discovery, an important challenge is to be able to control and manipulate them. Here, we propose a new mechanism to inject monopoles in a spin ice through a staggered magnetic field. We show theoretically, and demonstrate experimentally in the Ho$_2$Ir$_2$O$_7$ pyrochlore iridate, that it results in the stabilization of a monopole crystal, which exhibits magnetic fragmentation. In this new state of matter, the magnetic moment fragments into an ordered part and a persistently fluctuating one. Compared to conventional spin ices, the different nature of the excitations in this fragmented state opens the way to novel tunable field-induced and dynamical behaviors.

Published
2017

33. Preliminary Study for a New Axion Dark-Matter Haloscope

Author

Pugnat, P., Ballou, R., Camus, Ph., Caspers, F., Ko, B.R., Roch, N., Semertzidis, Y.K., Laboratoire national des champs magnétiques intenses - Grenoble (LNCMI-G ), 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 Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire national des champs magnétiques intenses - Grenoble (LNCMI), 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)-Université Joseph Fourier - Grenoble 1 (UJF)-Université Grenoble Alpes (UGA), Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), and Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)

Subjects
Astrophysics and Astronomy, axion: dark matter, 010308 nuclear & particles physics, dark matter: detector, magnet: superconductivity, sensitivity, 01 natural sciences, 7. Clean energy, cavity: microwaves, cryogenics, 0103 physical sciences, amplifier, quantum chromodynamics, electronics: readout, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], interference: quantum, Detectors and Experimental Techniques, 010306 general physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], detector: design
Abstract

Pugnat, P. "Preliminary Study for a New Axion Dark-Matter Haloscope" in 12th "Patras" Workshop on Axions, WIMPs and WISPs, PATRAS 2016 / Kim, Younglm, Lindner, Axel, Semertzidis, Yannis K. (eds.), Verlag Deutsches Elektronen-Synchrotron : 2017 ; PATRAS 2016 : 12th "Patras" Workshop on Axions, WIMPs and WISPs, 2016-06-20 - 2016-06-24, Jeju Island 12th Patras Workshop on Axions, WIMPs and WISPs, AXION-WIMP 2016, Jeju Island, South Korea, 20 Jun 2016 - 24 Jun 2016; Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-PROC, 129-132 (2017). doi:10.3204/DESY-PROC-2009-03/Pugnat_Pierre, A new haloscope for Axion dark-matter search is under study using in a first step the large bore superconducting magnet in construction at the LNCMI in Grenoble, which will produce 9~T in 812~mm diameter and 1400~mm height. Microwave cavities of high quality factor $Q\sim10^5-10^6$ will be developed at CAPP/IBS in Daejeon. Low-noise microwave amplification of the signal will be ensured by DC superconducting quantum interference devices (SQUID) or/and Josephson parametric amplifiers (JPA) cooled-down to 20~mK by a $^3$He/$^4$He dilution refrigerator. This new haloscope will be designed to probe QCD dark-matter Axions in the mass range of 1-100~$\mu$eV with unprecedented sensitivity., Published by Verlag Deutsches Elektronen-Synchrotron, Hamburg

Published
2017

34. Magnetic properties of the honeycomb oxide Na 2 Co 2 TeO 6

Author

Lefrançois, E., Songvilay, M., Robert, J., Nataf, G., Jordan, E., Chaix, L., Colin, Claire, Lejay, P., Hadj-Azzem, A., Ballou, R., Simonet, V., Magnétisme et Supraconductivité (MagSup ), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Matériaux, Rayonnements, Structure (MRS), and Cristaux Massifs (CrisMass)

Subjects
[PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2016

37. Synchrotron radiation for probing the quantum ground state in Tb2Ti2O7

Author

Constable, E., De Brion, S., Simonet, V., Robert, J., Ballou, R., Petit, S., Decorse, C., Brubach, J., Roy, Pascal, Magnétisme et Supraconductivité (NEEL - MagSup), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Groupe 3 axes (G3A), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Magnétisme et Supraconductivité (MagSup ), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Institut Rayonnement Matière de Saclay (IRAMIS), and Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat]
Abstract

International audience; When studying magnetic excitations, neutron spectroscopy is typically the method of choice. The low-energy and electromagnetic nature of terahertz radiation presents a new and complementary technique to probe exotic magnetic states. Here we perform terahertz spectroscopy on the quantum spin-ice candidate Tb 2 Ti 2 O 7 using standard and coherent synchrotron radiation. These novel measurements show fine structure and polarization dependent features that reveal new information about a possible vibronic ground state in Tb 2 Ti 2 O 7 and are complementary to existing neutron studies.

Published
2016

38. Magnetic properties of the honeycomb oxide Na$_2$Co$_2$TeO$_6$

Author

Lefran��ois, E., Songvilay, M., Robert, J., Nataf, G., Jordan, E., Chaix, L., Colin, C. V., Lejay, P., Hadj-Azzem, A., Ballou, R., and Simonet, V.

Subjects
Condensed Matter - Strongly Correlated Electrons, Strongly Correlated Electrons (cond-mat.str-el), FOS: Physical sciences, Condensed Matter::Strongly Correlated Electrons
Abstract

We have studied the magnetic properties of Na$_2$Co$_2$TeO$_6$, which features a honeycomb lattice of magnetic Co$^{2+}$ ions, through macroscopic characterization and neutron diffraction on a powder sample. We have shown that this material orders in a zig-zag antiferromagnetic structure. In addition to allowing a linear magnetoelectric coupling, this magnetic arrangement displays very peculiar spatial magnetic correlations, larger in the honeycomb planes than between the planes, which do not evolve with the temperature. We have investigated this behavior by Monte Carlo calculations using the $J_1$-$J_2$-$J_3$ model on a honeycomb lattice with a small interplane interaction. Our model reproduces the experimental neutron structure factor, although its absence of temperature evolution must be due to additional ingredients, such as chemical disorder or quantum fluctuations enhanced by the proximity to a phase boundary., 9 pages, 13 figures

Published
2016

39. Anisotropic interactions opposing magnetocrystalline anisotropy in Sr 3 NiIrO 6

Author

Lefrançois, E., Pradipto, A.-M., Moretti Sala, M., Chapon, L., Simonet, V., Picozzi, S., Lejay, P., Petit, S., Ballou, R., Magnétisme et Supraconductivité (MagSup ), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Politecnico di Milano [Milan] (POLIMI), and Cristaux Massifs (CrisMass)

Subjects
[PHYS.COND.CM-SCE]Physics [physics]/Condensed Matter [cond-mat]/Strongly Correlated Electrons [cond-mat.str-el], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2016

40. New Exclusion Limits for the Search of Scalar and Pseudoscalar Axion-Like Particles from 'Light Shining Through a Wall'

Author

Ballou, R., Deferne, G., Finger, M., Jr., Finger, M., Flekova, L., Hosek, J., Kunc, S., Macuchova, K., Meissner, K.A., Pugnat, P., Schott, M., Siemko, A., Slunecka, M., Sulc, M., Weinsheimer, C., and Zicha, J.

Subjects
High Energy Physics - Experiment (hep-ex), Physics - Instrumentation and Detectors, FOS: Physical sciences, Instrumentation and Detectors (physics.ins-det), Particle Physics - Experiment, High Energy Physics - Experiment
Abstract

Physics beyond the Standard Model predicts the possible existence of new particles that can be searched at the low energy frontier in the sub-eV range. The OSQAR photon regeneration experiment looks for "Light Shining through a Wall" from the quantum oscillation of optical photons into "Weakly Interacting Sub-eV Particles", such as axion or Axion-Like Particles (ALPs), in a 9 T transverse magnetic field over the unprecedented length of $2 \times 14.3$ m. In 2014, this experiment has been run with an outstanding sensitivity, using an 18.5 W continuous wave laser emitting in the green at the single wavelength of 532 nm. No regenerated photons have been detected after the wall, pushing the limits for the existence of axions and ALPs down to an unprecedented level for such a type of laboratory experiment. The di-photon couplings of possible pseudo-scalar and scalar ALPs can be constrained in the nearly massless limit to be less than $3.5\cdot 10^{-8}$ GeV$^{-1}$ and $3.2\cdot 10^{-8}$ GeV$^{-1}$, respectively, at 95% Confidence Level., 6 pages, 6 figures

Published
2015

41. Fragmentation in spin ice from magnetic charge injection

Author

Lefrançois, E., Cathelin, V., Lhotel, Elsa, Robert, J., Lejay, P., Colin, C. V., Canals, Benjamin, Damay, F., Ollivier, J., Fak, B., Chapon, L. C., Ballou, R., Simonet, V., Magnétisme et Supraconductivité (NEEL - MagSup), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Max Planck Institute for Solid State Research, Max-Planck-Gesellschaft, Institut Laue-Langevin (ILL), Croissance Cristalline et MicroAnalyse (NEEL - C2MA), Matériaux, Rayonnements, Structure (NEEL - MRS), Théorie de la Matière Condensée (NEEL - TMC), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), DIAMOND Light source, Magnétisme et Supraconductivité (MagSup ), ILL, Cristaux Massifs (CrisMass), Matériaux, Rayonnements, Structure (MRS), Théorie de la Matière Condensée (TMC ), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay

Subjects
[PHYS.PHYS.PHYS-ATOM-PH]Physics [physics]/Physics [physics]/Atomic Physics [physics.atom-ph], High Energy Physics::Lattice, Science, Condensed Matter::Strongly Correlated Electrons
Abstract

International audience; The complexity embedded in condensed matter fertilizes the discovery of new states of matter, enriched by ingredients like frustration. Illustrating examples in magnetic systems are Kitaev spin liquids, skyrmions phases, or spin ices. These unconventional ground states support exotic excitations, for example the magnetic charges in spin ices, also called monopoles. Here, we propose a mechanism to inject monopoles in a spin ice at equilibrium through a staggered magnetic field. We show theoretically, and demonstrate experimentally in the Ho2Ir2O7 pyrochlore iridate, that it results in the stabilization of a monopole crystal, which exhibits magnetic fragmentation. In this new state of matter, the magnetic moment fragments into an ordered part and a persistently fluctuating one. Compared to conventional spin ices, the different nature of the excitations in this fragmented state opens the way to tunable field-induced and dynamical behaviors

Published
2017

42. Results and Perspectives for Laboratory Search of Weakly Interacting Sub-eV Particles with the OSQAR Experiment

Author

Pugnat, P., Ballou, R., Schott, M., Husek, T., Sulc, M., Deferne, G., Duvillaret, L., Finger, M., Flekova, L., Hosek, J., Jary, V., Jost, R., Kral, M., Kunc, S., Macuchova, K., Meissner, K. A., Morville, J., Romanini, D., Siemko, A., Slunecka, M., Vitrant, G., Zicha, J., Magnétisme et Supraconductivité (MagSup), Institut Néel (NEEL), 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)-Université Joseph Fourier - Grenoble 1 (UJF), Kapteos SAS, LAsers, Molécules et Environnement (LAME-LIPhy), Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères] (LIPhy), Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Technical University of Liberec, University of Liberec, Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Institut de Microélectronique, Electromagnétisme et Photonique - Laboratoire d'Hyperfréquences et Caractérisation (IMEP-LAHC), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)

Subjects
Experiment, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Phenomenology, Cosmology and Extragalactic Astrophysics, High Energy Physics, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Astrophysics
Abstract

Recent intensive theoretical and experimental studies highlight the possibility of new fundamental particle physics beyond the standard model that can be probed by sub-eV energy experiments. The OSQAR photon regeneration experiment looks for Light Shining through a Wall (LSW) from the quantum oscillation of optical photons into Weakly Interacting Sub-eV Particles (WISPs), like axion or axion-like particles (ALPs), in a 9 T transverse magnetic field over the unprecedented length of 2 x 14.3 m. No excess of events has been detected over the background. The di-photon couplings of possible new light scalar and pseudo-scalar particles can be constrained in the massless limit to be less than 8.0 x 10-8 GeV-1. These results are very close to the most stringent laboratory constraints obtained for the coupling of WISPs to two photons. Plans for further improving the sensitivity of the OSQAR experiment are presented.

Published
2014

43. Latest Results of the OSQAR Photon Regeneration Experiment for Axion-Like Particle Search

Author

Ballou, R., Deferne, G., Duvillaret, L., Finger, Jr., M., Finger, M., Flekova, L., Hosek, J., Husek, T., Jary, V., Jost, R., Kral, M., Kunc, S., Macuchova, K., Meissner, K. A., Morville, J., Pugnat, P., Romanini, D., Schott, M., Siemko, A., Slunecka, M., Sulc, M., Vitrant, G., Weinsheimer, C., Zicha, J., 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), European Organization for Nuclear Research (CERN), Charles University [Prague] (CU), Czech Technical University in Prague (CTU), Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères] (LIPhy), Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Technical University of Liberec, Institute of Theoretical Physics [Warsaw], Faculty of Physics [Warsaw] (FUW), University of Warsaw (UW)-University of Warsaw (UW), Institut Lumière Matière [Villeurbanne] (ILM), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon, Laboratoire national des champs magnétiques intenses - Grenoble (LNCMI-G), Centre National de la Recherche Scientifique (CNRS)-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, Johannes Gutenberg - Universität Mainz (JGU), Institut de Microélectronique, Electromagnétisme et Photonique - Laboratoire d'Hyperfréquences et Caractérisation (IMEP-LAHC), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Université Joseph Fourier - Grenoble 1 (UJF)-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), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics - Instrumentation and Detectors, Cosmology and Nongalactic Astrophysics (astro-ph.CO), 010308 nuclear & particles physics, FOS: Physical sciences, Physics::Optics, Instrumentation and Detectors (physics.ins-det), 01 natural sciences, High Energy Physics - Experiment, High Energy Physics - Phenomenology, High Energy Physics - Experiment (hep-ex), High Energy Physics - Phenomenology (hep-ph), 0103 physical sciences, [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex], 010306 general physics, Particle Physics - Experiment, ComputingMilieux_MISCELLANEOUS, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Ballou, Rafik "Latest Results of the OSQAR Photon Regeneration Experiment for Axion-Like Particle Search" in Proceedings, 10th Patras Workshop on Axions, WIMPs and WISPs (AXION-WIMP 2014) / Tsesmelis, Emmanuel, Maroudas, Marios (eds.), Verlag Deutsches Elektronen-Synchrotron : 2014 ; AXION-WIMP 2014 : 10th Patras Workshop on Axions, WIMPs and WISPs, 2014-06-29 - 2014-07-04, Geneva 10th Patras Workshop on Axions, WIMPs and WISPs, AXION-WIMP 2014, Geneva, Switzerland, 29 Jun 2014 - 4 Jul 2014 ; DESY-PROC 125-130(2014). doi:10.3204/DESY-PROC-2014-03/pugnat_pierre, The OSQAR photon regeneration experiment searches for pseudoscalar and scalar axion-like particles by the method of ``Light Shining Through a Wall'', based on the assumption that these weakly interacting sub-eV particles couple to two photons to give rise to quantum oscillations with optical photons in strong magnetic field. No excess of events has been observed, which constrains the di-photon coupling strength of both pseudoscalar and scalar particles down to $5.7 \cdot 10^{-8}$ GeV$^{-1}$ in the massless limit. This result is the most stringent constraint on the di-photon coupling strength ever achieved in laboratory experiments., Published by Verlag Deutsches Elektronen-Synchrotron, Hamburg

Published
2014
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44. Results and Perspectives for Laboratory Search of Weakly Interacting Sub-eV Particles with the OSQAR Experiment

Author

Pugnat, P., Ballou, R., Schott, M., Husek, T., Sulc, M., Deferne, G., Duvillaret, L., Finger, M., Jr., Finger, M., Flekova, L., Hosek, J., Jary, V., Jost, R., Kral, M., Kunc, S., Macuchova, K., Meissner, K.A., Morville, J., Romanini, D., Siemko, A., Slunecka, M., Vitrant, G., and Zicha, J.

Subjects
Particle Physics - Experiment
Abstract

Recent intensive theoretical and experimental studies highlight the possibility of new fundamental particle physics beyond the standard model that can be probed by sub-eV energy experiments. The OSQAR photon regeneration experiment looks for Light Shining through a Wall (LSW) from the quantum oscillation of optical photons into Weakly Interacting Sub-eV Particles (WISPs), like axion or axion-like particles (ALPs), in a 9 T transverse magnetic field over the unprecedented length of 2 x 14.3 m. No excess of events has been detected over the background. The di-photon couplings of possible new light scalar and pseudo-scalar particles can be constrained in the massless limit to be less than 8.0 x 10-8 GeV-1. These results are very close to the most stringent laboratory constraints obtained for the coupling of WISPs to two photons. Plans for further improving the sensitivity of the OSQAR experiment are presented. Recent theoretical and experimental studies highlight the possibility of new fundamental particle physics beyond the Standard Model that can be probed by sub-eV energy experiments. The OSQAR photon regeneration experiment looks for “Light Shining through a Wall” from the quantum oscillation of optical photons into “Weakly Interacting Sub-eV Particles”, like axion or axion-like particles (ALPs), in a 9 T transverse magnetic field over the unprecedented length of $2 \times 14.3$ m. No excess of events has been detected over the background. The di-photon couplings of possible new light scalar and pseudo-scalar particles can be constrained in the massless limit to be less than $8.0\times 10^{-8}$ GeV$^{-1}$ . These results are very close to the most stringent laboratory constraints obtained for the coupling of ALPs to two photons. Plans for further improving the sensitivity of the OSQAR experiment are presented. Recent theoretical and experimental studies highlight the possibility of new fundamental particle physics beyond the Standard Model that can be probed by sub-eV energy experiments. The OSQAR photon regeneration experiment looks for "Light Shining through a Wall" (LSW) from the quantum oscillation of optical photons into "Weakly Interacting Sub-eV Particles" (WISPs), like axion or axion-like particles (ALPs), in a 9 T transverse magnetic field over the unprecedented length of $2 \times 14.3$ m. No excess of events has been detected over the background. The di-photon couplings of possible new light scalar and pseudo-scalar particles can be constrained in the massless limit to be less than $8.0\times10^{-8}$ GeV$^{-1}$. These results are very close to the most stringent laboratory constraints obtained for the coupling of ALPs to two photons. Plans for further improving the sensitivity of the OSQAR experiment are presented.

Published
2013

45. Dzyaloshinsky-Moriya driven helical-butterfly structure in Ba3NbFe3Si2O14

Author

Scagnoli, V., Huang, S. W., Garganourakis, M., de Souza, R. A., Staub, U., Simonet, V., Lejay, P., and Ballou, R.

Subjects
Condensed Matter - Strongly Correlated Electrons, Strongly Correlated Electrons (cond-mat.str-el), FOS: Physical sciences, Condensed Matter::Strongly Correlated Electrons
Abstract

We have used soft x-ray magnetic diffraction at the Fe3+ L2,3 edges to examine to what extent the Dzyaloshinsky-Moriya interaction in Ba3NbFe3Si2O14 influences its low temperature magnetic structure. A modulated component of the moments along the c-axis is present, adding to the previously proposed helical magnetic configuration of co-planar moments in the a,b-plane. This leads to a helical-butterfly structure and suggests that both the multi-axial in-plane and the uniform out-of-plane Dzyaloshinsky-Moriya vectors are relevant. A non zero orbital magnetic signal is also observed at the oxygen K edge, which reflects the surprisingly strong hybridization between iron 3d and oxygen 2p states, given the nominal spherical symmetry of the Fe3+ half filled shell.

Published
2013

50. Summary of OSQAR First Achievements and Main Requests for 2008

Author

Ballou, R, Barbara, B, Duvillaret, L, Jost, R, Finger, M, Hošek, J, Meissner, K A, Pugnat, P, Siemko, A, Šulc, M, and Zicha, J

Subjects
ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Detectors and Experimental Techniques
Abstract

In the first paragraph, OSQAR foremost achievements are summarised together with a brief reminder of its scientific context. In the second paragraph, activities planned for 2008 are briefly reviewed including the expected scientific results. The third paragraph is devoted to the requests addressed to CERN as the host laboratory and as a collaboration member of the OSQAR photon regeneration experiment.

Published
2007

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