Magnetism and Superconductivity

Goals

The MagSup team was born from the fusion in 2014 of three teams of experimentalists working on condensed matter physics, from fundamental properties to applications. Over the last five years, we have strengthened our ties within the team while the diversity of cultures of the three original groups allowed novel fruitful approaches. Our team is the largest of the Neel Institute, with 25 CNRS and University researchers and more than 10 student and post-docs.

The research activity of the team can be decomposed into four main topics:

• Applied superconductivity
• Fundamental superconductivity
• Electronic correlations
• Magnetism

Our objective is to understand and to manipulate the fundamental properties, which emerge from microscopic interactions and or from the interplay between several degrees of freedom (charge, spin, orbital, lattice) in a great variety of strongly correlated electrons systems. These are materials such as transition metals oxides, compounds of actinides or rare-earths, or disordered systems. These systems exhibit unconventional properties of magnetism, superconductivity, charge orderings, with several coexisting orders sometimes strongly coupled and/or in competition due to magnetic frustration. Our microscopic understanding of the fundamental states and associated excitations is established in strong connection with theoreticians and allows us, in collaboration with chemists, to foresee and study in depth new systems. Eventually, we simulate and manipulate the functionalities of these materials to create new devices.

We also develop an original instrumentation in the laboratory and use large scale facilities (neutron sources, synchrotron, intense magnetic field), in extreme conditions of magnetic fields, (low) temperature and pressure. The team is perfectly established in its Grenoble environment. It interacts narrowly through experimental developments and joint doctoral and scientific projects, within Institut Néel, but also with the LNCMI, G2Elab, CEA’s IRIG teams and European large scale facilities, ESRF and ILL. We also play an essential role in structuring and animating local, national and international science in organising seminars, conferences and schools, but also in participating in commissions and management positions.

Overview of applied superconductivity

Our approach is transversal from elaboration/chemistry and physical characterizations to the realization, implementation and tests of large-scale models or major demonstrators through functional property characterizations (transport, AC losses…), design and modeling. The collaboration of different research activities (material, simulation of physical properties) aims to understand the materials and physics in view to better innovating devices and to adapt or optimize the material properties in function of the targeted applications. We have an important action in the scientific animation of the applied superconductivity community both on national and international levels.

• High-Tc superconducting coils
• High-Tc superconducting fault current limiter
• Modeling of High-Tc materials
• Kinetic inductance detectors (KIDs)

High-Tc superconducting coils

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High-Tc superconducting fault current limiters

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Modeling of high-Tc materials

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Kinetic inductance detectors (KIDs)

Associated staff: Florence Levy-Bertrand (MagSup), Thierry Klein (MagSup), Pierre Rodière (MagSup), Alessandro Monfardini (Helfa), Alain Benoit (Helfa), Johannes Goupy (Helfa), Martino Calvo (Cryogénie), Philippe Camus (Cryogénie).

Student: Usasi Chowdhury (Helfa).

Kinetic Inductance Detectors (KIDs) are a particular implementation of superconducting resonators. Superconducting microwaves resonators are superconducting thin films deposited onto insulating substrates patterned into LC circuits. Their resonance frequency is 2Πf = (LC)^-1/2 and they can achieved quality factor up to few millions. The KID detector has been proposed by the Caltech-JPL group in 2001. Photon detection is realized by monitoring variations of the resonance frequency. The incident light breaks down Cooper pairs, modifying the kinetic inductance L and thus the resonance frequency.

We develop KIDs (mainly) for millimeter wave observations in astrophysics, particles detection and fundamental superconductivity studies.

Collaborations: IRAM, LPSC, IPAG (Grenoble), IRAM (Granada), LAM (Marseille), LLAMA Consortium (Brazil-Argentina), APC (Paris), IAS, CSNSM (Orsay), Cardiff University (UK), SRON (Holland) , CAB (Madrid), Arizona State University (US), CNES, IRAP (Toulouse), Università di Roma, KIT (Karlsruhe), LAHC (Chambery), CEA-Irfu (Saclay).

Links:

Highlights 2017 : New SKID-detectors: a world below the superconducting gap

Highlights 2016 :  NIKA2: revolutionary camera for millimeter waves sees first light

Highlights 2014 :  New mm-wave instrument (”NIKA”) opens for astronomers

Selected publications:

Contact-less phonon detection with massive cryogenic absorbers, Johannes Goupy, J. Colas, M. Calvo, J. Billard, P. Camus, R. Germond, A. Juillard, L. Vagneron, M. De Jesus, F. Levy-Bertrand and A. Monfardini, Appl. Phys. Lett. 115, 223506 (2019). [APL, ArXiv]

Electrodynamics of granular aluminum from superconductor to insulator: observation of collective superconducting modes, F. Levy-Bertrand, T. Klein, T. Grenet, O. Dupre, A. Benoît, A. Bideaud, O. Bourrion, M. Calvo, A. Catalano, A. Gomez, J. Goupy, L. Grunhaupt, U. v. Luepke, N. Maleeva, F. Valenti, I. M. Pop, and A. Monfardini, Physical Review B 99, 094506 (2019). [PRB, ArXiv]

The NIKA2 large-field-of-view millimetre continuum camera for the 30 m IRAM telescope, R. Adam, A. Adane, P.A.R. Ade, P. André, A. Andrianasolo, H. Aussel, A. Beelen, A. Benoit, A. Bideaud, N. Billot, O. Bourrion, A. Bracco, M. Calvo, A. Catalano, G. Coiffard, B. Comis, M. De Petris, F.-X. Désert, S. Doyle, E.F.C. Driessen, R. Evans, J. Goupy, C. Kramer, G. Lagache, S. Leclercq, J.-P. Leggeri, J.-F. Lestrade, J.-F. Macias-Perez, P. Mauskopf, F. Mayet, A. Maury, A. Monfardini, S. Navarro, E. Pascale, L. Perotto, G. Pisano, N. Ponthieu, V. Reveret, A. Rigby, A. Ritacco, C. Romero, H. Roussel, F. Ruppin, K. Schuster, A. Sievers, S. Triqueneaux, C. Tucker, R. Zylka, A&A, vol. 609, p. A115 (2018). [AA, ArXiv]

Tunable sub-gap radiation detection with superconducting resonators, O. Dupré, A. Benoît, M. Calvo, A. Catalano, J. Goupy, C. Hoarau, T. Klein, K. Le Calvez, B. Sacépé, A. Monfardini and F. Levy-Bertrand, Supercond. Sci. Technol. 30, 045007 (2017). [SST, ArXiv]

Overview of fundamental superconductivity

Superconductivity is a state of matter corresponding to zero electrical resistance and magnetic field expulsion occurring in some materials cooled down below a critical temperature. Microscopically, it corresponds to a condensate of electron pairs. Such a condensate of fermions can occurred only because electron paired up to form Cooper pairs. In conventional superconductors, the glue binding the electron pairs is the exchange of lattice vibrations: the phonons.

Counterintuitively the materials achieving the highest critical temperatures at ambiant pressure are not the metallic ones, but rather ceramic materials: the high temperature superconductors or cuprates. A priori, the conventional electron-phonon coupling mechanism cannot explain Cooper pairing in cuprates.. Unraveling the mystery of the physical mechanism leading to high temperature superconductivity remains one of the most challenging issues of modern solid-state physics. 

In order to unveil the mechanism leading to high temperature superconductivity we look at different family of compounds by means of complementary probes. Indeed, in many strongly correlated electron systems, from heavy fermions to pnictides, including high temperature superconductors, superconductivity seems to be linked to the vicinity of an electronic or magnetic instability. The nature of the instability varies, ranging from antiferromagnetic order, to charge or spin density waves, including a pseudo-gap state or a metamagnetic transition. Those observations suggest that electronic or magnetic fluctuations may be involved in the pairing mechanism. The general aim is to determine the microscopic ingredients involved in both the formation of superconductivity and the electronic/magnetic states of each families.

• Higgs mode in superconductors
• Superconductivity in high-Tc cuprates
• Iron-based superconductivity
• Heavy fermions: magnetism and superconductivity
• Charge density waves and superconductivity
• Superconductivity and disorder

Higgs mode in superconductors

Associated staff: Marie-Aude Méasson (MagSup), Florence Levy-Bertrand (MagSup)

Student: Gregory Setnikar (MagSup)

Collective modes which emerge at a quantum phase transition are fundamental witnesses of their underlying quantum electronic phase. Notably for the superconducting state, they are expected to provide crucial information on its symmetry, on the pairing mechanism, on the effect of disorder, or on the interplay with coexisting electronic phases. Besides one of these modes, the fluctuations of the amplitude of the superconducting order parameter, is a historical analogous of the Higgs boson which still remains elusive to experimental validation. 

 In this growing field of research, our approach is to look for and to study sub-gap superconducting modes thanks to state-of-the-art spectroscopic probes, Raman and sub-THz spectroscopy.

Notably, in the field of disorder superconductors, we provide direct evidence for well resolved sub-gap absorptions in superconducting granular aluminium thanks to an original high resolution optical spectroscopy technique. We demonstrated two different types of sub-gap excitations below twice the superconducting gap 2∆, occurring at ω1 ≈ ∆ and ∆ < ω2 < 2∆. The nature of these excitations is unclear and under investigation.

In the quest of superconducting Higgs modes, we demonstrate that its observation could rely on the presence of an electron-phonon-coupled quantum order (charge density wave) coexisting with the superconductivity, whose collective mode couples to the Higgs one. It thus yields a signature in the Raman probe. Two examples are now present in the literature (Cf. ref. below), both in the dichalcogenides family. Our goal (ERC project HiggS²) is to fully address the Higgs mode nature and mechanism of observability in a variety of superconducting systems using Raman probe under extreme conditions.

Collaborations: Lara Benfatto (La Sapienza, Rome), Ioan Pop (KIT, Karlsruhe), Eugenio Coronado (ICMol, University of Valencia), Laurent Cario (IMN, Nantes).

Selected publications:

Pressure induced collapse of the charge density wave and Higgs mode visibility in 2H-TaS₂, Grasset, Y. Gallais, A. Sacuto, M. Cazayous, S. Mañas-Valero, E. Coronado and M.-A. Méasson, Phys. Rev. Lett. 122, 127001 (2019). [PRL, ArXiv]

Electrodynamics of granular aluminum from superconductor to insulator: observation of collective superconducting modes, F. Levy-Bertrand, T. Klein, T. Grenet, O. Dupre, A. Benoît, A. Bideaud, O. Bourrion, M. Calvo, A. Catalano, A. Gomez, J. Goupy, L. Grunhaupt, U. v. Luepke, N. Maleeva, F. Valenti, I. M. Pop, and A. Monfardini, Physical Review B 99, 094506 (2019). [PRB, ArXiv]

Circuit Quantum Electrodynamics of Granular Aluminum Resonators, N. Maleeva,  L. Grünhaupt, T. Klein,  F. Levy-Bertrand, O. Dupré, M. Calvo, F. Valenti, P. Winkel,  F. Friedrich, W. Wernsdorfer,  A. V. Ustinov, H. Rotzinger,  A. Monfardini,  M. V. Fistul, and I. M. Pop, Nature Communications 9, 3889 (2018). [Nat. Com., ArXiv]

Higgs-mode radiance and charge-density-wave order in 2H-NbSe₂, Grasset, T. Cea, Y. Gallais, M. Cazayous, A. Sacuto, L. Cario, L. Benfatto and M.-A. Méasson, Phys. Rev. B 97, 094502 (2018). [PRB, ArXiv]

Fundings:

ERC grant HiggS² (2020-2025) : Superconducting Higgs mode

ANR SEO-HiggS²  (2017-2021)

Superconductivity in high-Tc cuprates

Associated staff: Thierry Klein, Mattéo d’Astuto, Manuel Nunez-Regueiro, Christophe Marcenat (CEA)

The discovery of a charge ordered phase associated to a major Fermi surface reconstruction in underdoped cuprates recently revived the debate on the pairing mechanism in high-Tc superconductors, still one of the most challenging issue in modern solid-state physics.

Indeed, as in most of the unconventional materials, high-Tc superconductivity appears in the vicinity of a competing instability, but in the case of cuprates, not one but several instabilities compete with the superconducting phase, including this charge ordered phase, antiferromagnetic and spin ordered phases as well as a still very enigmatic pseudo-gap phase. 

The three central phenomena of high-Tc cuprate are then linked by a common doping p* around which the superconducting phase forms a dome, the resistivity exhibits an anomalous linear dependence on temperature and where the pseudo-gap phase ends. However, the fundamental nature of p* remains unclear, in particular whether it marks a true quantum phase transition is still debated.

Unravelling the mystery goes through a better understanding of the normal state giving rise to superconductivity. Unfortunately, superconductivity is very robust and studying this normal state requires for instance the use of very high magnetic fields and hence of instrumental probes adapted to those extreme conditions. 

We performed extensive studies of the normal state electronic contribution to the specific heat in various cuprates. We have then recently shown that the interplay between superconductivity and the charge ordered phase leads to an unusual S-shape of the transition line between the superconducting and normal states, indicating that those two exclusive orders finally establish a form of cooperation in order to coexist at low T. 

We also showed that the Sommerfeld coefficient displays a pronounced peak in the vicinity of p* in several cuprates (at very low temperature), associated with a logT dependence of the specific heat, two classical features of the existence of a quantum critical point (QCP). The broken symmetry associated to this possible QCP is still unknown but the (quantum) fluctuations could be involved in both d-wave pairing and the anomalous scattering of charge carriers.

Another approach consists in looking to a model systems: cuprates oxychlorides. Oxychlorides are unique among the high temperature superconducting cuprates (HTSCs) since they:  lacks high Z atoms; have a simplest crystalline structure for cuprates, stable at all doping and temperatures; and have a strong 2D character due to the replacement of apical oxygen with chlorine. Therefore, advanced calculations that incorporate correlation effects, such as Quantum Monte Carlo and Dynamical Mean Field Theory (DMFT) are easier. However, relatively little is known about Ca2CuO2Cl2 from an experimental point of view. We are now filling this gap by a comprehensive experimental study covering the whole phase diagram, in particular of the magnon and phonon dispersion as well as their electronic structure, using advanced approaches based on synchrotron and laboratory spectroscopies. In this context, a particular experimental effort has been focused recently in probing their elusive bulk charge ordered phase, and related excitation, using Resonant Inelastic X-ray Scattering.

Tools:

• Specific heat measurements
• Magnetic measurements
• Transport measurements (incl. high pressure)
• Resonant and non-resonant Inelastic X-ray Scattering
• Inelastic Neutron Scattering
• Diffraction

Main Collaborations:

• France: A. Demuer and D. Leboeuf (LNCMI-Grenoble), S. Biermann (Ecole Polytechnique – College de France), B. Lenz (IMPMC, Paris).
• International: L. Taillefer [and collaborators] (Université de Sherbrooke), J. Kacmarcik (Slovak Academy of Sciences), A. Rydh (University of Stockholm), C. Meingast [and collaborators] (Karlsruhe Institute of Technology), I. Yamada (Osaka Prefecture University), M. Azuma (Tokyo Institute of Technology), M. Dean (Brookhaven National Laboratory).

Links:

Highlights 2016: The enigmatic normal state of high temperature superconductors

Highlights 2019: The enigmas of high temperature superconductivity

Selected publications:

Iron-based superconductivity

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Heavy fermions : magnetism and superconductivity

Associated staff: Carley Paulsen, Klaus Hasselbach, Pierre Rodière, Marie-Aude Méasson, Florence Lévy-Bertrand

Heavy-fermion systems are intermetallic materials composed of rare earths (Ce, Yb) or actinides (U,…) elements. In these systems, partially filled 4f- or 5f-electron orbitals are strongly-coupled to conduction-electrons bands. Electronic interactions give rise to the formation of heavy quasiparticles, i.e., narrow electronic bands with a strong enhancement of the effective mass m∗ , which typically reaches 100 to 1000 times the value of the free-electron mass m0. Since their discovery in the 1980’, more and more heavy-fermion compounds are founds that are superconducting, some are even ferromagnetic and superconducting simultaneously. Heavy-fermion compounds are expected to host spin triplet superconductivity, equal spin pairing, and to present effects of topology, chirality and potentially edge states. Heavy-fermions are ideal platforms to study fundamental concepts of Quantum Matter.

Figure 1: Magnetization vs field for UTe2 at 100 mK and 1 K, below the superconducting transition temperature at 1.5 K just above Tc. Superconductivity is arising from a large paramagnetic background. Inset comparison of UTe2 with the ferromagnetic superconductors UCoGe and URhGe just above their respective Tc, their remanent magnetization is clearly distinctive from the paramagnetic state of UTe2. Physical Review B 103, L180501 (2021).

Figure 2: Scanning SQUID image at T=900 mK of magnetic flux structures in PdTe2. At 30 G, the configuration minimizing the total electromagnetic energy is a triangular lattice of normal tubes funneling magnetic flux (orange) through the otherwise superconducting (purple) crystal. PdTe2 is a Weyl semimetal and a type-I superconductor. Physical Review B 103, 104510 (2021).

Tools:

• Low Field SQUID magnetometer and susceptometer operating at temperatures as low as 60 mK at frequencies between 0.1mHz and 1 kHz: 7 orders of magnitude
• High Field SQUID magnetometer  operating at temperatures as low as 60 mK and magnetic fields as high as 9 teslas
• Scanning SQUID microscopy operating at temperatures as low as 150 mK with a spatial resolution of 500 nm and a magnetic resolution of 550 microG/Hz0.5

These unique instruments were built by us and are part of the European MicroKelvin Platform.

Left : microSQUID microscope (Height 130 mm). More in Zhao Sheng Wang’s thesis. Right : microSQUID microscope image of individual vortices in a square Nb pattern (light green) 80 micrometer * 80 micrometer.

Main Collaborations:

• France: Jean-Pascal Brison, Georg Knebel, Daniel Braithwaite (CEA Grenoble, UGA), Ilya Sheikin (LNCMI CNRS Grenoble),  Sébastien Burdin (Loma Univ. Bordeaux CNRS);
• International: D. Aoki (Tohoku University Japan),  Anne de Visser (University of Amsterdam Pays Bas), S. R. Giblin (Cardiff University, United Kingdom), C. Geibel (Dresden Max Planck).

Links (if nothing appears, look in your download folder):

Highlights 2006: Magnetic Imaging of unconventional superconductors

Highlights 2018: Scanning Hall Probe microscopy

Selected publications:

Type-I superconductivity in the Dirac semimetal PdTe₂, H. Leng, C. Paulsen, Y. Huang, A. de Visser, Physical Review B 96, 220506 (2017). [PRB, HAL]

Visualization by scanning SQUID microscopy of the intermediate state in the superconducting Dirac semimetal PdTe₂, P. Garcia-Campos, Y. Huang, A. de Visser, Klaus Hasselbach, Physical Review B 103, 104510 (2021) [PRB, HAL]

MicroSQUID Force microscopy in a dilution refrigerator, Danny Hykel, Zhao-Sheng Wang, Pauline Castellazzi, Thierry Crozes, Gorky Shaw et al., Journal of Low Temperature Physics 175, 861 (2014). [JLTP, HAL]

Pairing mechanism in the ferromagnetic superconductor UCoGe, Beilun Wu, Gael Bastien, Mathieu Taupin, Carley Paulsen, Ludovic Howald, Dai Aoki, Jean-Pascal Brison, Nature Comm. 8, 14480 (2017). [NatCom, HAL]

Determination of spin and orbital magnetization in the ferromagnetic superconductor UCoGe, M. W. Butchers, J. A. Duffy, J. W. Taylor, S. R. Giblin, S. B. Dugdale, C. Stock, P. H. Tobash, E. D. Bauer, C. Paulsen, Physical Review B 92, 121107(R) (2015). [PRB, Condmat]

Magnetic and superconducting phase diagram of the half-Heusler topological semimetal HoPdBi, A. M. Nikitin, Y. Pan, X. Mao, R. Jehee, G. K. Araizi, Y. K. Huang, C. Paulsen, S. C. Wu, B. H. Yan, A. de Visser, J. Phys.: Condens. Matter 27, 275701 (2015). [JPCM, Condmat]

Magnetic fields above the superconducting ferromagnet UCoGe, D. Hykel, C. Paulsen, D. Aoki, J. R. Kirtley, Klaus Hasselbach, Physical Review B 90, 184501 (2014). [PRB, HAL]

Low field magnetic response of the non-centrosymmetric superconductor YPtBi, T. V. Bay, M. Jackson, C. Paulsen, C. Baines, A. Amato, T. Orvis, M. C. Aronson, Y. K. Huang, A. de Visser, Solid State Communications 183, 13 (2014). [SSC, Condmat]

Superconductivity and magnetic order in the non-centrosymmetric Half Heusler compound ErPdBi, Y. Pan, A. M. Nikitin, T. V. Bay, Y. K. Huang, C. Paulsen, B. H. Yan, A. de Visser, Europhysics Letters 104, 27001 (2013). [EPL, Condmat]

Observation of the Meissner-Ochsenfeld Effect and the Absence of the Meissner State in UCoGe, Carley Paulsen, Danny Hykel, Klaus Hasselbach, Dai Aoki, Physical Review Letters 109, 237001 (2012). [PRL, HAL]

Field-Induced Phenomena in Ferromagnetic Superconductors UCoGe and URhGe, D. Aoki, M. Taupin, C. Paulsen, F. Hardy, V. Taufour et al., J. Phys. Soc. Jpn 81, SB002 (2012). [JPSJ, HAL]

CDW and superconductivity

Associated staff: Pierre Rodière, Manolo Núñez-Regueiro, Marie-Aude Méasson, Christine Opagiste

A charge density wave is a Fermi surface instability due to a large electronic susceptibility in metallic systems. This long range order induces the opening of a gap at the Fermi level to reduce the electronic energy. Thanks to an electron-phonon coupling, the charge density wave is associated to a lattice distortion. Both phenomena modify strongly the electronic structure of the system. This distortion gives often rise to an aperiodic structure and a peculiar lattice dynamic. Moreover, by applying an external tuning parameter the lattice distortion can be tuned to 0K inducing a quantum phase transition. Numerous of these metallic systems exhibit also superconducting properties at proximity of this quantum phase transition.

Several fundamental questions raised in these systems. What is the role of the aperiodic structure of the system and the breakdown of the Bloch theorem? How is the phase diagram of these systems? What are the consequences of the presence of the soft phonon modes on the superconducting state? How the disorder affects these orders? What are the emerging excitations of the coexistence of the charge density wave and the superconductivity?  What is the influence of the dimensionality? What laws govern the quantum phase transition from CDW to superconductivity under an external parameter such as pressure? What is the role of CDW’s in high temperature superconducting cuprates?

In the MagSup team, we are studying these phenomena on a large number of systems ranging from the transition metal dichalchogenides, to intermetallic with or without strong electronic couplings. We are growing single crystal and using transport, thermodynamic and spectroscopy techniques in extreme of low temperature and high pressures conditions.

Phase diagram of 2H-NbSe2. Inset atomic resolution scanning tunneling microscopy showing the Moiré effect due to the CDW. CDW and superconductivity coexist up to 4GPa. Superconductivity is not strongly affected by the soft phonon mode at the origin of the CDW (adapted from Phys. Rev. B 92 (2015) 140303(R)).

Tools:

• Transport under pressure
• Raman spectroscopy
• Inelastic X-ray scattering
• Neutron spectroscopy
• Magnetic penetration depth measurements
• Crystal synthesis

Links:

International Research Network : Aperiodic

Highlight 2016 : Influence of lattice vibrations on quantum phase transitions

Publications:

Superconductivity and disorder

Associated staff: Florence Levy-Bertrand (MagSup), Thierry Klein (MagSup), Hervé Cercellier (MagSup), Christophe Marcenat (MagSup), Etienne Bustarret (SC2G), Julien Pernot (SC2G), Xavier Blase (TMC), Benjamin Sacépé (QuNES).

Counterintuitively, at ambient pressure, the materials achieving the highest critical temperatures are not the metallic ones, but rather ceramic materials. The high Tc or cuprates look like slate and copper or gold show no sign of superconductivity. Such observations suggest that superconductivity is a subtle balance between the electronic density, the electronic interactions (Coulomb repulsion and Coulomb screening) and the electron-phonon coupling (or some electron-boson coupling).

Besides the intrinsic materials properties, disorder can turn a superconductor into an insulator resulting in an electrical resistance spanning all the way from zero to infinity. The physical mechanism triggering the transition between those two states of matter is still highly debated. Superconductivity is not affected by a small amount of disorder but strong disorder gives rise to unscreened coulomb repulsions generating classic Anderson insulating states, possible electron glass states, or Cooper-pair insulators (see associated part in electronic correlation section). Even more puzzling, in some superconductors, moderate disorder can even enhanced superconductivity.  Such observations encourage the study of the effect of electronic scattering on superconductivity.

We explore the influence of these different parameters (electronic density, electronic interactions, electron-phonon coupling and electronic scattering) through the introduction of disorder or through the variation of charge carriers by chemical doping. Lately we studied granular aluminum, B-doped silicon and B-doped diamond. We employed transport measurements, optical spectroscopy and point contact spectroscopy.

Granular aluminum films are formed of superconducting nanometric grains of pure aluminum separated by oxide barriers. The coupling between grains can then be varied by changing the oxygen pressure during the Al evaporation, and this material can also be tuned from a superconductor to an insulator. Surprisingly, the critical temperature first rises (getting larger than in pure aluminium) before decreasing as the superconductor to insulator transition is approached, hence displaying a dome. By combining transport and state-to-the-art high resolution optical spectroscopy measurements, we have provided evidence for well resolved sub-gap absorptions, showing up in the vicinity of maximum of the superconducting dome. The nature of these excitations is still unclear but offers a unique opportunity to investigate the interplay between Josephson energy, Coulomb repulsion and superconducting coupling.

Phase diagram of granular aluminum from PRB 99, 094506 (2019). Top panel: Zoom on the superconducting transition of the resistivity measurements as a function of temperature. Bottom panel: Critical temperatures versus room temperature resistivity.

A detailed study of boron-doped diamond epilayers show that the boron concentration corresponding to the onset of superconductivity does not coincide with that of the metal-insulator transition.

Phase diagram of B-doped diamond from PRB 95, 161301 (R) (2017). kF l value (a), critical temperature (b), and residual conductivity (c) as a function of boron doping in C:B epilayers.

Collaborations: Ioan Pop (KIT, Karlsruhe), Jozef Kacmarcik (Slovak Academy of Sciences), Shimpei Ono (CRIEPI, Tokyo).

Selected publications:

Electrodynamics of granular aluminum from superconductor to insulator: observation of collective superconducting modes, F. Levy-Bertrand, T. Klein, T. Grenet, O. Dupre, A. Benoît, A. Bideaud, O. Bourrion, M. Calvo, A. Catalano, A. Gomez, J. Goupy, L. Grunhaupt, U. v. Luepke, N. Maleeva, F. Valenti, I. M. Pop, and A. Monfardini, Physical Review B 99, 094506 (2019). [PRB, ArXiv]

Circuit Quantum Electrodynamics of Granular Aluminum Resonators, N. Maleeva,  L. Grünhaupt, T. Klein,  F. Levy-Bertrand, O. Dupré, M. Calvo, F. Valenti, P. Winkel,  F. Friedrich, W. Wernsdorfer,  A. V. Ustinov, H. Rotzinger,  A. Monfardini,  M. V. Fistul, and I. M. Pop, Nature Communications 9, 3889 (2018). [Nat. Com., ArXiv]

Phase diagram of B-doped diamond revisited by thickness-dependent magneto-transport, J.Bousquet, T.Klein, M.Solana, L.Saminadayar, C.Marcenat and E.Bustarret, Physical Review B, Rapid Communication 95, 161301(R) (2017). [PRB, HAL]

Overview of electronic correlations

This research activity is focused on the unusual electronic states which exist when electrons are correlated. A variety of physical situations are investigated : electrons in low dimensional systems (Luttinger liquid in carbon nanotubes, electronic instabilities in quasi-1D or 2D crystals) ; peculiar charge, orbital and magnetic orders in 3D correlated systems (magnetite, multiferroics) ; electron Coulomb glass state in highly disordered systems.

• Charge-density-waves
• Charge order in magnetite
• Glassy dynamics in disordered insulators
• Many-body localization

Charge-density-waves

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Charge order in magnetite

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Glassy dynamics in disordered insulators

Associated staff: Thierry Grenet and Julien Delahaye.

During the past twenty years, a few experimental groups in the world have observed that in some disordered insulators and at low temperature, the application of a gate voltage or of other perturbations induce very slow (days long) relaxations of the electrical conductance. These were suggested to be the first experimental evidences of the « electron glass ». Glasses are systems with such a slow internal dynamics that they cannot reach their thermodynamic equilibrium within any experimentally accessible time. Famous examples in condensed matter are structural and spin glasses. It was theoretically suggested in the 80ies, that the electrons can « freeze » at low temperature in disordered insulators (Anderson insulators) due to the coexistence of disorder and ill-screened electron-electron interactions, giving rise to the so-called electron glass. We aim to characterize these slow relaxations and to understand their nature: do they really reflect the existence of a glassy state? Is this glass the electron glass or something else? Are the glassy features common to all disordered insulating systems?

Figure 1: three disordered systems investigated. Left: granular Al (TEM picture, Marie-Claude Cheynet, SiMaP). Middle: discontinuous Au (SEM picture). Right: amorphous NbSi (TEM picture, CSNSM).

To answer such questions, we first focused on the conductance relaxations of insulating granular Al films, an archetype of disordered insulators in which nanometric Al grains are embedded in an amorphous alumina matrix (see the left image on Fig. 1). We demonstrated that the slow dynamics observed at 4 K depends on the age of the system, i.e. the time elapsed since its cool down at low temperature (see Fig. 2) [Grenet et al, Eur. Phys. J. B 76 229 (2010)]. This property called « ageing » is characteristic of glassy systems and found for example in spin and structural glasses. We also developed non-isothermal gate voltage protocols that allowed us to reveal the non-trivial thermally activated character of the glassy dynamics [Grenet et al, Eur. Phys. J. B. 56 183 (2007); Grenet et al, J. Phys. Cond. Matt. 29 455602 (2017)].

Figure 2: relaxations of a granular Al film conductance after a gate voltage change at 4.2 K and for different ages of the system. The amplitude of the relaxation is larger in « young » films than in « old » ones.

We are currently exploring in a wide range of resistance and temperature (4 K – 300 K) other insulating systems of different disorder realizations: amorphous NbSi (in collaboration with Claire Marrache-Kikuchi’s group in Orsay), amorphous indium oxide films and discontinuous gold films (in collaboration with Aviad Frydman’s group in Tel Aviv). Our first results reveal that most of the glassy features, such as ageing and thermal activation of the dynamics, are robust and shared by all the systems [Delahaye et al, SciPost Phys. 8 056 (2020)].

Collaborations: Claire Marrache-Kikuchi’s group, CSNSM, Orsay ; Aviad Frydman’s group, Bar-Ilan University, Tel-Aviv ; Miguel Ortuño’s group, Murcia University, Murcia.

Selected publications:

Anomalous electric field and glassy behaviour in granular aluminium thin films: electron glass?, T. Grenet, J. Delahaye, M. Sabra and F. Gay, Eur. Phys. J. B 56, 183 (2007). [EPJB, arXiv]

Manifestation of ageing in the low temperature conductance of disordered insulators, T. Grenet and J. Delahaye, Eur. Phys. J. B 76, 229 (2010). [EPJB, arXiv]

Manifestation of ageing in the low temperature conductance of disordered insulators, T. Grenet and J. Delahaye, Eur. Phys. J. B 76, 229 (2010). [EPJB, arXiv]

Evidence for thermal activation in the glassy dynamics of insulating granular aluminium conductance, T. Grenet and J. Delahaye, Journal of Physics Condensed Matter 29, 455602 (2017). [JPCondMat, arXiv]

Electron glass effects in amorphous NbSi, J. Delahaye, T. Grenet, C. Marrache-Kikuchi, V. Humbert, L. Bergé and L. Dumoulin, SciPost Phys. 8 056 (2020). [SciPost, arXiv]

Many body localization in cooper-pair insulators

Associated staff:  Thierry Grenet (MagSup), Julien Delahaye (MagSup) and Benjamin Sacépé (QuNES).

PhD Student: Thibault Charpentier (QuantECA).

The problem of localization of quantum particles by disorder is a long-standing one. It was pioneered by P. W.  Anderson in 1958 who discovered that disorder can localize non-interacting degrees of freedom. However little progress was made concerning the effect of mutual interactions, like e.g. the coulomb repulsion between electrons in disordered solids. 

Ten years ago a theoretical breakthrough was achieved. It was shown that a system of interacting fermions put in a static disordered potential, totally isolated from any external thermal bath, may experience a transition from an equilibrium metallic phase to a localized non ergodic one when the temperature is reduced below a critical Tc. The transition was coined many-body localization (MBL).

This prediction has far reaching implications. First it is a fundamental progress in the basic question about the conditions under which isolated quantum systems can thermalize without the help of any external bath, and comply with equilibrium statistical mechanics. It also predicts the existence of an unprecedented kind of insulator which possesses an exactly zero conductivity (in the infinite system limit) in a finite temperature interval T < Tc.

Although these findings sparked a tremendous theoretical activity, a clear experimental demonstration of MBL is still missing.

In this project we propose to search for this new phenomenon in Cooper-pair insulators. These are systems possessing Cooper pairs localized by disorder. A prototypical case is amorphous (a) indium oxide under magnetic field. In this system, it was shown that electrons are efficiently decoupled from phonons at low temperature. Moreover in the Cooper-pair insulator phase, the resistance shows a divergence at finite temperature, an expected hallmark of MBL.

These first results are very promising and much broader investigations are now needed to more surely identify and study the aspects of the MBL. With our project partners, we propose to investigate the different aspects of the transition using dielectric (Institut Néel) and thermoelectric measurements (LPEM), as well as to search for the non-ergodic features expected to appear near and across Tc (Institut Néel). These studies will be complemented by the characterization and measurements of a second promising candidate material: insulating a-YSi (CSNSM). These investigations will be conducted in close interaction with theoretical analyses (LPTHE).

Project partners: Lev Ioffe and Lara Faoro (LPTHE, Orsay) ; Claire Marrache-Kikuchi, Shamashis Sengupta, Louis Dumoulin, Laurent Bergé and Marnieros Stefanos (CSNSM, Orsay) ; Kamran Behnia and Benoit Fauqué (LPEM, Paris).

Funding: ANR (2019-2023).

Overview of magnetism

Beyond simple collinear ferromagnets and antiferromagnets, a wealth of remarkable properties is observed in bulk magnetic materials like oxides, molecular magnets or intermetallics, containing rare-earth and/or transition metals atoms. The ingredients favoring complexity and hence interesting behaviors are (i) the magnetic frustration either arising from competing interactions or from the geometry of the lattice based for instance on triangles (kagome), on tetrahedra (pyrochlore), or on pentagons, (ii) the presence of several degrees of freedom like spin, orbit, lattice or charge, (iii) the low dimensionality of the magnetic lattice.

• Magnetism in low dimensions
• Magnetism of cage compounds
• Magnetic frustration
• Multiferroism and magnetoelectric coupling
• Magnetocaloric materials
• Vacuum magnetism and Weakly Interacting Sub-eV Particles (WISPs)

Magnetism in low dimensions

Associated staff: R. Ballou, S. de Brion, E. Lhotel, E. Lorenzo, C. Paulsen,  J. Robert, V. Simonet.

Former non-permanent staff: E. Lefrançois, Q. Faure, E. Constable.

The reduction of dimensionality in bulk magnetism is due to the existence of a hierarchy of interactions, i.e. the magnetic coupling is much stronger in one or two spatial directions than in the remaining ones. This can lead to 2D, 1D (spin chains) or even 0D (single molecule magnets) magnetic arrangements, which are model systems for studying cooperative magnetic phenomena in presence or absence of long-range magnetic ordering. In particular, additional ingredients such as magnetic frustration, strong spin-orbit coupling, or quantum effects induce exotic ground states (e.g. spin liquid state) dressed with excitations that may have no counterpart in conventional 3D magnets (e.g. spinons) with specific defects (0D or 1D domain-walls) and topological properties.

Experimentally, the systems we are interested in are oxide compounds, but also molecular magnets in which the magnetic topology can be designed thanks to the versatile arrangement of molecular building blocks. We study their magnetic properties using specific instrumentation down to very low temperatures (< 100 mK magnetometry and specific heat) as well as large-scale facilities (neutron scattering and synchrotron X-ray). This allows us to probe precisely their unconventional phase diagram and the associated excitations, as a function of magnetic field, pressure and temperature.

As example, we have evidenced long-distance spin entanglement in the spin ladder/spin chain cuprate Sr₁₄Cu₂₄O₄₁. We have also unveiled novel magnetic field-induced (topological) quantum phase transitions in the spin chain compound BaCo₂V₂O₈.

Some collaborations: T. Giamarchi (Univ. Geneva, Switzerland), S. Takayosi (Konan University, Kobe, Japan), S. Petit (LLB), B. Grenier, C. Marin, S. Raymond, L.P. Regnault (INAC CEA Grenoble), L. Chapon (Diamond, UK), M. Moretti (Politecnico di Milano), A. Revcolevschi (Orsay), S. Sahling (TU Dresden), R. Sibille (PSI, Switzerland), J.-P. Sutter (LCC, Toulouse), ….

Publications:

The high field magnetisation of FePS₃, A. R. Wildes, D. Lançon, M. K. Chan, F. Weikert, N. Harrison, V. Simonet, M. Zhitomirsky, M. Gvodikova, T. Ziman and H. Rønnow, Physical Review B 101, 024415 (2020). [PRB]

Tomonaga-Luttinger Liquid Spin Dynamics in the Quasi-One-Dimensional Ising-Like Antiferromagnet BaCo₂V₂O₈,  Q. Faure, S. Takayoshi, V. Simonet, B. Grenier, M. Månsson, J. White, G. Tucker, C. Rüegg, P. Lejay, T. Giamarchi and S. Petit, Physical Review Letters, 123, 027204 (2019). [arXiv, PRL]

Low-Temperature Heat Capacity of Sr₂Ca₁₂Cu₂₄O₄₁, S. Sahling, J. E. Lorenzo, G. Remenyi and V. L. Katkov, J Low Temp Phys, 194, 142 (2018). [JLowTempPhys]

Polarized-neutron investigation of magnetic ordering and spin dynamics in BaCo₂(AsO₄)₂ frustrated honeycomb-lattice magnet, L.P. Regnault, C. Boullier and J.E. Lorenzo, Heliyon 4, e00507 (2018). [arXiv, Heliyon]

Generalized Ramsey interferometry explored with a single nuclear spin qudit, C. Godfrin, R. Ballou, E. Bonet, M. Ruben, S. Klyatskaya, W. Wernsdorfer and F. Balestro, npj Quantum Information 4, 53 (2018). [npj]

Topological quantum phase transition in the Ising-like antiferromagnetic spin chain BaCo₂V₂O₈, Q. Faure, S. Takayoshi, S. Petit, V. Simonet, S. Raymond, L.-P. Regnault, M. Boehm, J. S. White, M. Månsson, Ch. Rüegg, P. Lejay, B. Canals, T. Lorenz, S. C. Furuya, T. Giamarchi and B. Grenier, Nature Physics, 14, 716 (2018). [arXiv, NatPhys]

The magnetic properties and structure of the quasi-two-dimensional antiferromagnet CoPS₃, A. R. Wildes, V. Simonet, E. Ressouche, R. Ballou and G. J. McIntyre, J. Phys. : Condens. Matter 29, 455801 (2017). [arXiv, JPhysCondMatt]

Operating Quantum States in Single Magnetic Molecules: Implementation of Grover’s Quantum Algorithm,
C. Godfrin, A. Ferhat, R. Ballou, S. Klyatskaya, M. Ruben, W. Wernsdorfer and F. Balestro, Phys. Rev. Lett. 119, 187702 (2017). [PRL]

Magnetic properties of the honeycomb oxyde Na₂Co₂TeO₆, E. Lefrançois, M. Songvilay, J. Robert, G. Nataf, E. Jordan, L. Chaix, R. Ballou, C. V. Colin, P. Lejay, A. Hadj-Azzem and V. Simonet, Physical Review B 94, 214416 (2016). [PRB]

Anisotropic interactions opposing magnetocrystalline anisotropy in Sr₃NiIrO₆, E. Lefrançois, A.-M. Pradipto, M. Moretti Sala, L. C. Chapon, V. Simonet, S. Picozzi, P. Lejay, S. Petit and R. Ballou, Physical Review B 93, 224401 (2016). [arXiv, PRB]

The magnetic structure of the quasi-two dimensional antiferromagnet NiPS₃, A. R. Wildes, V. Simonet, E. Ressouche, G. McIntyre, M. Avdeev, E. Suard, S. Kimber, D. Lançon, G. Pepe, B. Moubaraki and T. J. Hicks, Physical Review B, 92, 224408 (2015). [HAL, PRB]

Neutron diffraction investigation of the H−T phase diagram above the longitudinal incommensurate phase of BaCo₂V₂O₈, B. Grenier, V. Simonet, B. Canals, P. Lejay, M. Klanjsek, M. Horvatik and C. Berthier, Physical Review B, 92, 134416 (2015). [HAL, PRB]

Experimental realization of long-distance entanglement between spins in antiferromagnetic quantum spin chains, S. Sahling, G. Remenyi, C. Paulsen, P. Monceau, V. Saligrama, C. Marin, A. Revcolevschi, L. P. Regnault, S. Raymond and J. E. Lorenzo, Nature Physics 11, 255 (2015). [Nature Phys.]

Longitudinal and transverse Zeeman ladders in the Ising-like chain antiferromagnet BaCo₂V₂O₈, B. Grenier, S. Petit, V. Simonet, L.-P. Regnault, E. Canévet, S. Raymond, B. Canals, C. Berthier and P. Lejay, Physical Review Letters, 114, 017201 (2015). [arXiv, PRL]

On the importance of ferromagnetic exchange between transition metals in field-free SMMs : examples of ring-shaped hetero-trimetallic [(LnNi₂)W(CN)₈]₂ compounds , S. Dhers, J.P. Costes, P. Guionneau, C. Paulsen, L. Vendier and J.-P. Sutter,  Chem. Commun. 51, 7875 (2015). [Chem. Comm.]

Magnetic order in the frustrated Ising-like chain compound Sr₃NiIrO₆, E. Lefrançois, L. C. Chapon, V. Simonet, P. Lejay, D. Khalyavin, S. Rayaprol, E. V. Sampathkumaran, R. Ballou and D. T. Adroja, Physical Review B, 90, 014408 (2014). [arXiv, PRB]

Electrically driven nuclear spin resonance in single-molecule magnets, S. Thiele, F. Balestro, R. Ballou, S. Klyatskaya, M. Ruben and W. Wernsdorfer, Science 344, 1135 (2014). [Science]

Adding Remnant Magnetization and Anisotropic Exchange to Propeller-like Single-Molecule Magnets through Chemical Design, K.C.M. Westrup, M.E. Boulon , P. Totaro, G.G. Nunes, D.F. Back, A. Barison, M. Jackson, C. Paulsen, D. Gatteschi, L. Sorace, A. Cornia, J.F. Soares and R. Sessoli, Chemistry – A European Journal 20, 13681 (2014). [Chem. A Eur. J.]

[Mn-III(Schiff Base)]₃[Re-IV(CN)₇], Highly Anisotropic 3D Coordination Framework : Synthesis, Crystal Structure, Magnetic Investigations, and Theoretical Analysis, D.G. Samsonenko, C. Paulsen, E. Lhotel, V.S. Mironov and K.E. Vostrikova, Inorg. Chem. 53, 10217 (2014). [Inorg. Chem.]

Magnetic structure and dynamics of a strongly one-dimensional cobalt(II) metal-organic framework, R. Sibille, E. Lhotel, T. Mazet, B. Malaman, C. Ritter, V. Ban and M. François, Physical Review B  89, 104413 (2014). [arXiv, PRB]

Magnetism of cage compounds

Cette page est vide.

Magnetic frustration

Associated staff: R. Ballou, S. de Brion, E. Lhotel, C. Paulsen, J. Robert, V. Simonet, M. Songvilay

Non permanent staff: Y. Alexanian, M. Léger, F. Museur

Magnetic structure and excitations in Fe langasite

The guiding principle of our research is the quest for new magnetic phases of matter. In this respect, magnetic frustration, stemming either from the geometry of the lattice, or from competition between different kinds of magnetic interactions, may lead to very wide range of exotic phenomena and magnetic states, that can be ordered (ex. non-collinear, chiral) or disordered (ex. spin liquids, spin ices, where the competing interactions prevents the system from conventional magnetic ordering).

Understanding, characterizing and classifying this novel states of matter, having non-trivial static and dynamical correlations, is one of the main goal of the current research in frustrated systems : degeneracy of the ground-state ? stability against quantum fluctuations ? broken symmetry and underlying order parameter (nematic order, topological order, etc.) ? elementary excitations (local soft modes, fractional bosonic excitations such as spinons and “magnetic monopoles”, etc.) ? Role of the competition/cooperation between several degrees of freedom (spin, orbit, lattice, charge) ?

Experimentally, answering these questions requires a combination of complementary probes developed at the Institut Néel or based on large scale facilities : magnetometry, neutron and X-ray scattering under extreme conditions (very low temperatures, high magnetic fields). Using these techniques, we mainly focus our attention on classical and quantum properties of lattices based on corner-sharing triangles or tetraedra or other geometries (pentagons). The experimental results are confronted to models in a fructuous comings and goings through collaborations with theoreticians. This activity is also based on the use of high quality materials, in particular single-crystals, and therefore relies on a synthesis work realized inside or outside the laboratory.

Some collaborations:

Institut Néel : MRS and TMC teams
Others : E. Ressouche, S. Raymond, M. Zhitomirsky (INAC CEA Grenoble), S. Petit, F. Damay (LLB), S. Giblin (Cardiff University, UK), K. Matsuhira (Kyushu, Japan), R. Sibille (PSI, Switzerland), P. Holdsworth (ENS Lyon), L. C. Chapon (Diamond), P.P. Deen (ESS, Sweden), M. Ciomaga Hatnean, G. Balakrishnan (Univ. Warwick)

Some recent publications

Dimer physics in the frustrated Cairo pentagonal antiferromagnet Bi₂Fe₄O₉
K. Beauvois, V. Simonet, S. Petit, J. Robert, F. Bourdarot, M. Gospodinov, A. A. Mukhin, R. Ballou, V. Skumryev, E. Ressouche, Phys. Rev. Lett. 124, 127202 (2020). [Phys. Rev. Lett., arXiv]

Multiferroism and magnetoelectric coupling

Associated staff: M. Amara, R. Ballou, S. de Brion, J. Robert, V. Simonet.

Present non permanent staff: Y. Alexanian.

Former non-permanent staff: M. Loire, L. Chaix (PhD), E. Constable (Post-doc), C. Eggenspiller, J. Scoarnec (Master).

The combination of several ferroic orders (ferroelectric, ferromagnetic, ferroelastic, ferrotoroidic and their antiferro- couterparts) in the same material, coined under the term of multiferroics, has received a lot of attention for more than one decade. Multiferroics indeed open the way to the electric-field control of magnetic dipoles and the converse magnetic-field control of electric dipoles in a number of future hybrid technologies (for instance novel electronics based on spins and charges). This electric/magnetic cross-manipulation, based on the magnetoelectric effect, can be at play at the static level allowing the electric/magnetic manipulation of magnetic/ferroelectric/ferrotoroidic domains for instance. It can also have signatures on the elementary excitations emerging from the ordered states of matter in the form of hybrid excitations called electromagnon that are now perceived as an electric charge dressing of magnons. This dressing enables the electric-field control of magnons and is thus foreseen to be used in magnonics, a new information science using magnetic excitations to carry and process information. In this context, the search for other new kinds of magnetoelectric excitations and of new mechanisms enabling the electroactivity of magnons is a key issue.

In our team, we search for novel multiferroic materials and novel properties associated to the coupling between various orders. We also study the magnetoelectric coupling at the dynamical level by combining sophisticated techniques implying the use of large-scale facilities such as inelastic neutron scattering and THz spectroscopy on a synchrotron source.

Tools

At Néel Institute:

• magnetization and specific heat measurements;
• electric polarization measurements under magnetic field up to 8 T;
• optical spectroscopy.

Large scale facilities:

• neutron scattering : diffraction, inelastic, use of polarized neutrons and polarization analysis (ILL, LLB and other neutron sources);
• THz Spectroscopy (synchrotron@SOLEIL).

Main collaborations

• Institut Néel: MRS and TMC teams, pôle cristaux massifs, pôle automatisation et caractérisation, pôle Ingénierie expérimentale.
• Others: S. Petit, F. Damay (LLB, France), P. Roy, J.-B. Brubach, M. Verseils (SOLEIL, France), L.-P. Regnault, E. Ressouche, S. Raymond, F. Bourdarot (CEA, France), A. Wildes, J. Ollivier, O. Fabello, L. Cañadillas-Delgado (ILL, France), M. Cazayous (Université Paris Diderot, France), M. Guennou (Luxembourg), U. Staub, V. Scagnoli (Switzerland), G. Nilsen (United Kingdom), G. Quirion (Canada)…

Links:

Highlight 2015: TeraHertz properties of multiferroic compounds

Highlight 2013: TeraHertz magneto-electric excitations in a chiral material

Publications:

Incommensurate spin ordering and excitations in multiferroic SrMnGe₂O₆, C. V. Colin, L. Ding, E. Ressouche, J. Robert, N. Terada, F. Gay, P. Lejay, V. Simonet, C. Darie, P. Bordet and S. Petit, Phys. Rev. B 101, 235109 (2020). [PRB]

Archetypal soft-mode driven antipolar transition in francisite Cu₃Bi(SeO₃)₂O₂Cl, C. Milesi-Brault, C. Toulouse, E. Constable, H. Aramberri, V. Simonet, S. de Brion, H. Berger, L. Paolini, A. Bosak, J. Iñiguez  and M. Guennou, Phys. Rev. Lett. 124, 097603 (2020). [PRL, ArXiv]

Effects of Ca substitution on quasi-acoustic sliding modes in Sr_14-xCaxCu₂₄O₄₁, E. Constable, A.D. Squires, J. Horvat, R.A. Lewis, D. Appadoo, R. Plathe, P. Roy, J.-B. Brubach, S. deBrion, A. Pimenov and G. Deng, Phys. Rev. B 100, 1843005 (2019). [PRB, Arxiv]

Interplay between spin dynamics and crystal field in the multiferroic compound HoMnO₃, X. Fabrèges, S. Petit, J.-B. Brubach, P. Roy, M. Deutsch, A. Ivanov, L. Pinsard-Gaudart, V. Simonet, R. Ballou and S. de Brion, Phys. Rev. B 100, 094437 (2019). [PRB, ArXiv]

Field-induced double spin spiral in a frustrated chiral magnet, M. Ramakrishnan, E. Constable, A. Cano, M. Mostovoy, J. S. White, N. Gurung, E. Schierle, S. de Brion, C. V. Colin, F. Gay, P. Lejay, E. Ressouche, E. Weschke, V. Scagnoli, R. Ballou, V. Simonet and U. Staub, Nature Physical Journal, Quantum Materials 4, 60 (2019). [NaturePhysQM, ArXiv]

Single-crystal neutron diffraction study of hexagonal YbMnO₃ under magnetic field, S. Chattopadhyay, V. Simonet, V. Skumryev, A.A. Muhkin, V. Ivanov, D.Z. Dimitrov, M. Gospodinov and E. Ressouche, Phys. Rev. B 98, 134413 (2018). [PRB, arXiv]

Microscopic Insights on the Multiferroic Perovskite‐Like [CH₃NH₃][Co(COOH)₃] Compound, L. Mazzuca, L. Cañadillas‐Delgado, O. Fabelo, J.A. Rodríguez‐Velamazán, J. Luzón, O. Vallcorba, V. Simonet, C.V. Colin and J. Rodríguez‐Carvajal, Chemistry – A European Journal 24, 388 (2018). [ChemEurJ]

Field driven magnetostructural transitions in GeCo₂O₄, X. Fabrèges, E. Ressouche, F. Duc, S. de Brion, M. Amara, C. Detlefs, L. Paolasini, E. Suard, L.-P. Regnault, B. Canals, P. Strobel and V. Simonet,  Phys. Rev. B 95, 014428 (2017). [PRB]

Magnetic and dielectric order in the kagomelike francisite Cu₃Bi(SeO₃)₂O₂Cl, E. Constable, S. Raymond, S. Petit, E. Ressouche, F. Bourdarot, J. Debray, M. Josse, O. Fabelo, H. Berger, S. deBrion and V. Simonet, Phys. Rev. B 96, 014413 (2017). [PRB, ArXiv]

Experimental evidences of symmetry breaking in the multiferroic Ba₃NbFe₃Si₂O₁₄ using sound velocity measurements, G. Quirion, C. Bidaud, J. Quilliam, P. Lejay, V. Simonet and R. Ballou,  Phys. Rev. B 96, 134433 (2017). [PRB]

Crystal Symmetry Lowering in Chiral Multiferroic Ba₃TaFe₃Si₂O₁₄ observed by X-Ray Magnetic Scattering, M. Ramakrishnan, Y. Joly, Y. W. Windsor, L. Rettig, A. Alberca, E. M. Bothschafter, R. Ballou, V. Simonet, P. Lejay, V. Scagnoli and U. Staub, Phys. Rev. B 95, 205145 (2017). [PRB, HAL]

Phase diagram of multiferroic KCu₃As₂O₇(OD)₃, J. Nilsen, V. Simonet, C.V. Colin, R. Okuma, Y. Okamoto, M. Tokunaga,T.C. Hansen, D.D. Khalyavin and Z. Hiroi  , Phys. Rev. B 95, 214415 (2017). [PRB, ArXiv]

One-dimensional short-range magnetic correlations in the magnetoelectric pyroxene CaMnGe₂O₆, L. Ding, C.V. Colin, C. Darie, J. Robert, F. Gay and P. Bordet, Phys. Rev. B 93, 064423 (2016). [PRB]

Helical bunching and symmetry lowering inducing multiferroicity in Fe langasites, L. Chaix, R. Ballou, A. Cano, S. Petit, S. de Brion, J. Ollivier, L.-P. Regnault, E. Ressouche, E. Constable, C.V. Colin, A. Zorko, V. Scagnoli, J. Balay, P. Lejay and V. Simonet, Phys. Rev. B 93, 214419 (2016). [PRB]

Phonons in the multiferroic langasite Ba₃NbFe₃Si₂O₁₄: Evidence for symmetry breaking, C. Toulouse, M. Cazayous, S. de Brion, F. Levy-Bertrand, H. Barkaoui, P. Lejay, L. Chaix, M.B. Lepetit, J.B. Brubach and P. Roy, Phys. Rev. B 92, 104302 (2015). [PRB]

Magneto- to electro-active transmutation of spin waves in ErMnO₃, L. Chaix, S. de Brion, S. Petit, R. Ballou, L.-P. Regnault, J. Ollivier, J.-B. Brubach, P. Roy, J. Debray, P. Lejay, A. Cano, E. Ressouche and V. Simonet, Phys . Rev. Lett. 112, 137201 (2014). [PRL]

Lattice and spin excitations in multiferroic h-YMnO₃, C. Toulouse, J. Liu, Y. Gallais, M.-A. Measson, A. Sacuto, M. Cazayous, L. Chaix, V. Simonet, S. de Brion, L. Pinsard-Godart, F. Willaert, J.B. Brubach, P. Roy and S. Petit, Phys. Rev. B 89, 094415 (2014). [PRB]

Helical order and multiferroicity in the S = 1/2 quasi-kagome system KCu₃As₂O₇(OD)₃, J. Nilsen, Y. Okamoto, H. Ishikawa, V. Simonet, C. Colin, L.C. Chapon, T. Hansen, H. Mutka and Z. Hiroi, Phys. Rev. B 89, 140412 (2014). [PRB, ArXiv]

THz Magneto-electric atomic rotations in the chiral compound Ba₃NbFe₃Si₂O₁₄, L. Chaix, S. de Brion ,F. Levy-Bertrand, V. Simonet, R. Ballou, B. Canals, P. Lejay, J.B. Brubach, G. Creff, F. Willaert, P. Roy and A. Cano, Phys . Rev. Lett. 110, 157208 (2013). [PRL]

The Role of Order-disorder Transitions in the Quest for Molecular Multiferroics : Structural and Magnetic Neutron Studies of a Mixed Valence Iron(II)-Iron(III) Formate Framework, L. Cañadillas-Delgado, O. Fabelo, J. A. Rodríguez-Velamazán, M.-H. Lemée-Cailleau, S.A. Mason, E. Pardo, F. Lloret, J.-P. Zhao, X.-H. Bu, V. Simonet, C. V. Colin and J. Rodríguez-Carvajal, J. Am. Chem. Soc., 134, 19772–19781 (2012). [JACS, HAL]

Magnetoelectric MnPS₃ as a candidate for ferrotoroidicity, E. Ressouche, M. Loire, V. Simonet, R. Ballou, A. Stunault and A. Wildes, Phys. Rev. B 82, 100408(R), Editor’s suggestion (2010). [PRB, ArXiv]

Magnetic and dielectric properties in the langasite-type compounds : A₃BFe₃D₂O₁₄ with A=Ba, Ca, Sr, B=Nb, Ta, Sb, and C=Si, Ge, K. Marty, P. Bordet, V. Simonet, M. Loire, R. Ballou, C. Darie, J. Kljun, P. Bonville, O. Isnard, P. Lejay, B. Zawilski and C. Simon, Phys. Rev. B 81, 054416 (2010). [PRB, ArXiv]

Magnetocaloric materials

Cette page est vide.

Vacuum Magnetism and Weakly Interacting Sub-eV Particles (WISPs)

Cette page est vide.

Experimental techniques

Présentation / Overview

Avec 7 maîtres de conférences et professeurs et 2 chercheurs CNRS avec une délégation partielle d’enseignement, notre équipe est fortement impliquée dans les cours et la formation des étudiants. Nous avons des responsabilités pédagogiques dans les parcours et les unités d’enseignement de l’école d’ingénieurs Grenoble-INP et de l’Université Grenoble Alpes. Nous donnons également des cours dans des écoles thématiques européennes (par exemple : European School of Magnetism, European School of Applied Superconductivity, Hercules, DRTBT, ISOE) et dans les formations continues en cryogénie organisées par le CNRS.

With seven professors and associate professors and two CNRS researchers with a partial delegation of teaching, the team is strongly involved in lectures and training of students. We have pedagogical responsibilities at the engineering school of Grenoble INP and at Grenoble Alpes University (UGA). We also give lectures in European or thematic schools (including European School of Magnetism, European School of Applied Superconductivity, Hercules, DRTBT, ISOE) and in continuous training in cryogenic organized by the CNRS.

Activités d’enseignement des membres de l’équipe :

• Thierry Klein, Professeur à l’UGA (page personnelle). Responsable de la mention de master en physique de 2012 à 2018 et actuellement en charge du parcours « matière quantique » de cette mention. Il est membre du conseil académique (commission formation et vie universitaire) de l’UGA.
• Christine Opagiste, Maître de Conférences à l’IUT1 de Grenoble, au département Mesures Physiques et en Licence Pro Capteur Instrumentation et Métrologie. Elle est membre élue depuis 2019 au Conseil National des Universités en 28ème section (CNU-28).

Formations niveau Master

Parcours « Matière Quantique » (UGA)

Responsable : Thierry Klein.

Grenoble est incontestablement un des principaux pôles mondiaux de recherche en physique de la matière condensée. C’est pourquoi l’Université Grenoble-Alpes propose depuis plusieurs décennies un parcours dédié à l’apprentissage de la physique de la matière condensée. Ce parcours baptisé « Matière Quantique » permet d’acquérir l’ensemble des outils conceptuels, expérimentaux et/ou numériques qui permettront de mieux comprendre les propriétés quantiques de la matière. Il est l’un des trois parcours de recherche fondamentale (RF) du master de Physique de l’UGA.

Liens :

• le site internet du parcours
• le programme à la rentrée 2021

A titre d’exemple, vous trouverez ci-dessous les présentations détaillées d’un certain nombre de cours donnés au sein de la mention physique par les enseignants de l’équipe :

• le cours de Mécanique Quantique (Master 1)
• le cours de Seconde Quantification (Master 2)