A5012121510- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Iron-based superconductors research
- Magnetic and transport properties of perovskites and related materials
- Rare-earth and actinide compounds
- Superconductivity in MgB2 and Alloys
- Superconducting Materials and Applications
- Magnetic properties of thin films
- High-pressure geophysics and materials
- Perovskite Materials and Applications
- Magnetic Field Sensors Techniques
- Organic and Molecular Conductors Research
- Acoustic Wave Resonator Technologies
- Methane Hydrates and Related Phenomena
- Amyloidosis: Diagnosis, Treatment, Outcomes
- Nuclear physics research studies
- Intellectual Capital and Performance Analysis
- Sensor Technology and Measurement Systems
- Gyrotron and Vacuum Electronics Research
- Multiferroics and related materials
- Magnetic Properties of Alloys
- Chalcogenide Semiconductor Thin Films
- Inorganic Fluorides and Related Compounds
- Random lasers and scattering media
- Earthquake Detection and Analysis
Université de Sherbrooke
2022-2024
University of Cambridge
2019-2023
University of British Columbia
2010-2016
The material $\alpha$-RuCl$_3$ has been the subject of intense scrutiny as a potential Kitaev quantum spin liquid, predicted to display Majorana fermions low energy excitations. In practice, undergoes transition state with antiferromagnetic order below temperature $T_{\rm N}$ $\approx$ 7 K, but this can be suppressed by applying an external in-plane magnetic field $H_\parallel$ = T. Whether liquid phase exists just above that is still open question, reported observation quantized thermal...
The 2D layered insulator $\alpha$-RuCl$_3$ is a candidate material for quantum spin-liquid state, which may be realized when magnetic field suppresses the antiferromagnetic order present at low temperature. Oscillations in dependence of thermal conductivity, observed an in-plane $B$ up to critical $B^{\star}$, have been attributed exotic charge-neutral fermions, viewed as evidence state between $B_{c}$ $\simeq 7$ T phase ends and $B^{\star}$. Here we report measurements conductivity function...
The recent detection of charge-density modulations in YBa2Cu3Oy and other cuprate superconductors raises new questions about the normal state underdoped cuprates. In one class theories, are intertwined with pairing a dual state, expected to persist up high magnetic fields as vortex liquid. support such specific heat magnetisation data on have been interpreted terms liquid persisting above vortex-melting field Hvs at T = 0. Here we report high-field measurements electrical thermal Hall...
A direct measurement of the London penetration depth in high-${T}_{c}$ superconductor ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{6.92}$ has been made using low-energy $\ensuremath{\mu}\text{SR}$ with an effective background suppression method. The average magnetic field versus mean was measured Meissner state high-purity detwinned crystals ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{6.92}$. resulting profiles along $a$ and $b$ axes are consistent a local model beyond 10 nm but there...
Abstract In various so-called strange metals, electrons undergo Planckian dissipation 1,2 , a strong and anomalous scattering that grows linearly with temperature 3 in contrast to the quadratic dependence expected from standard theory of metals. some cuprates 4,5 pnictides 6 linear resistivity on magnetic field has also been considered anomalous—possibly an additional facet dissipation. Here we show cuprate metals Nd 0.4 La 1.6− x Sr CuO 4 (ref. 7 ) 2− 8 is quantitatively consistent...
We report thermal conductivity measurements on single crystals of herbertsmithite, over a wide range temperatures (0.05-120 K) in magnetic fields up to 15 T. also the Hall effect, found be vanishingly small. At high temperatures, paramagnetic regime, has negligible field dependence. Upon cooling and development correlations, onset clear monotonic dependence below about 20 K signals new characteristic temperature scale that may reflect subtle crossover towards quantum spin liquid regime....
We have studied the microwave electrodynamics of single crystal iron-based superconductors Ba$_{0.72}$K$_{0.28}$Fe$_2$As$_2$ (hole-doped, $T_\mathrm{c}$ $\approx $30 K) and Ba(Fe$_{0.95}$Co$_{0.05}$)$_2$As$_2$ (electron-doped, $\approx$20 K), by cavity perturbation broadband spectroscopy. SQUID magnetometry was used to confirm quality homogeneity samples under study. Through techniques, temperature dependence in-plane London penetration depth $\Delta\lambda(T)$, therefore superfluid phase...
The absolute value and temperature dependence of the in-plane magnetic penetration depth $\ensuremath{\lambda}$ have been measured on a single crystal Ba(Co${}_{0.074}$Fe${}_{0.926}{)}_{2}$As${}_{2}$ using low-energy muon-spin rotation microwave cavity perturbation. field profiles in Meissner state are consistent with local London model beyond 15 nm. We determine gap symmetry through measurements superfluid density which follows two-gap $s$-wave over entire range below ${T}_{\mathrm{c}}$....
The Mott metal-insulator transition represents one of the most fundamental phenomena in condensed matter physics. Yet, basic tenets canonical Brinkman-Rice picture localization remain to be tested experimentally by quantum oscillation measurements that directly probe quasiparticle Fermi surface and effective mass. By extending this technique high pressure, we have examined metallic state on threshold clean, undoped crystals NiS2. We find i) approaching localization, mass is strongly...
The interaction with light weakens the superconducting ground state in classical superconductors. situation cuprate superconductors is more complicated: illumination increases charge carrier density, a photo-induced effect that persists below room temperature. Furthermore, systematic investigations underdoped YBa2Cu3O6+x (YBCO) have shown an enhanced critical temperature Tc. Until now, studies of photo-persistent conductivity (PPC) been limited to structural and transport properties, as well...
Interaction-enhanced carrier masses are central to the phenomenology of iron-based superconductors. Quantum oscillation measurements in new unconventional superconductor YFe_{2}Ge_{2} resolve all four Fermi surface pockets expected from band structure calculations, which predict an electron pocket Brillouin zone corner and three hole enveloping centers top bottom zone. Carrier reach up 20 times bare mass among highest ever observed any material, accounting for enhanced heat capacity...
The microwave conductivity of ultrapure single crystals ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{6.5}$ has been measured deep in the superconducting state as a continuous function frequency using broadband spectrometer. Conductivity spectra were first at four temperatures below 10 K after having prepared crystal so-called ortho-II phase, which Cu-O chain oxygens are ordered into alternating full and empty chains. These exhibit features expected for quasiparticle scattering from dilute...
We demonstrate a simple and easy-to-build probe designed to be loaded into widely available Quantum Design Physical Properties Measurement System (PPMS) cryostat, with detachable shielded sample puck section robust heat sinking of three pairs coaxial cables. It can in principle used any low-temperature cryostat. Our modular design has radiation shield for thermal isolation protection the delicate space while handling allows variety experimental setup benefiting from wiring constructed on...
Neutron scattering from high-quality ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.33}\phantom{\rule{0.28em}{0ex}}(\text{YBCO6.33})$ single crystals with a ${T}_{c}$ of 8.4 K shows no evidence coexistence superconductivity long-range antiferromagnetic order at this very low, near-critical doping $p\ensuremath{\sim}0.055$. However, we find short-range three-dimensional spin correlations that develop temperatures much higher than ${T}_{c}$. Their intensity increases smoothly on cooling...
With the advent of polarized low-energy muons, with tunable energy in kiloelectronvolt range, it is possible to use sensitivity and local-probe character µSR perform depth-dependent investigations on nanometer scale magnetic superconducting properties materials. Here, after a brief summary present status LE-µSR at PSI, we give some examples near-surface regions single crystals thin-film
In a growing number of materials, phonons have been found to generate thermal Hall effect, but the underlying mechanism remains unclear. Inspired by previous studies that revealed importance Tb$^{3+}$ ions in generating effect Tb$_{2}$Ti$_{2}$O$_{7}$, we investigated role Tm$^{3+}$ TmVO$_{4}$, paramagnetic insulator with different crystal structure. We observe negative conductivity TmVO$_{4}$ magnitude such angle, $|\kappa_{xy}$/$\kappa_{xx}|$, is approximately 1 x 10$^{-3}$ at $H$ = 15 T...
It has recently become clear that phonons generate a sizable thermal Hall effect in cuprates, whether they are undoped, electron-doped or hole-doped (inside the pseudogap phase). At higher doping, where cuprates reasonably good metals, mobile electrons also effect, equivalent of standard electrical effect. Here we show cleanest crystals cuprate Nd$_{2-x}$Ce$_{x}$CuO$_{4}$, at high phonon and electron contributions to conductivity $\kappa_{\rm {xy}}$ comparable magnitude, but opposite sign....
The absolute value and anisotropy of the magnetic penetration depth have been measured in a mosaic optimally-doped YBa2Cu3O6.92 crystals using low-energy muon spin rotation at 8 K with extrapolation to T = 0 microwave resonator data. average field was as function implantation energy small applied along â directions. Beyond d, profiles are consistent simple exponential decay internal expected from London model. results compared other less direct methods.
Quantum oscillation measurements in the new unconventional superconductor YFe$_2$Ge$_2$ resolve all four Fermi surface pockets expected from band structure calculations, which predict an electron pocket Brillouin zone corner and three hole enveloping centers of top bottom zone. The carrier masses are uniformly renormalized by about a factor five broadly account for enhanced heat capacity Sommerfeld coefficient $\simeq 100$ mJ/molK$^2$. Our data highlight key role pocket, despite its small...