arXiv subjects

T. Thebault

Publications and source records attributed to T. Thebault.

6 recordsLinked to original sources

arXiv2026

Fermi-liquid versus non-Fermi-liquid/'strange-metal' fits to the electrical resistivity in the quantum critical magnetic regime of an unconventional superconductor

The question of a possible quantum critical point lying inside of a superconducting phase is central for understanding unconventional superconductivity. In various unconventional superconductors, non-Fermi-liquid/'strange-metal' $T^{n}$ variations, with $n<2$, of the electrical resistivity have been identified as the signature of magnetic quantum criticality. However, a difficulty is to prove experimentally that a non-Fermi-liquid/'strange-metal' law identified at temperatures above the superconducting temperature is the signature of an intrinsic zero-temperature quantum critical regime. In the heavy-fermion paramagnet UTe$_2$, unconventional superconductivity develops in the vicinity of a metamagnetic quantum phase transition induced by a magnetic field, and the quantum critical magnetic properties are suspected to play a role for the superconducting mechanism. In this work, we present a comparative analysis of electrical resistivity data collected on two UTe$_2$ samples of different qualities, in magnetic fields tilted by angles $\theta\simeq35-40$~$^\circ$ from $\mathbf{b}$ to $\mathbf{c}$. Fits to the data have been performed either with a Fermi-liquid function $\rho=\rho_0+AT^{2}$ or with a non-Fermi-liquid/'strange-metal' function $\rho=\rho_0+A_nT^n$. Near to a superconducting phase induced beyond 40~T, non-physical residual resistivities $\rho_0<0$ are extracted from the $T^n$ fits, revealing that a 'hidden' Fermi-liquid $T^2$ regime may be ultimately recovered at low temperature. The results obtained here highlight the importance to investigate high-quality samples with low residual resistivity to confirm - or not - the presence of a suspected 'hidden' quantum critical behavior masked by superconductivity.

cond-mat.supr-con↗

arXiv2025

Anisotropic collapse of electronic correlations in the ferromagnet UGe$_2$ under high magnetic field

We present electrical-resistivity measurements on the prototypical heavy-fermion ferromagnet UGe$_2$ under pulsed magnetic field up to 60~T. An anisotropic field-induced suppression of the electronic correlations is revealed. The electrical resistivity strongly decreases when a magnetic field $\mathbf{H}$ is applied along the easy magnetic axis $\mathbf{a}$, while it remains almost unchanged when $\mathbf{H}$ is applied along the hard magnetic axes $\mathbf{b}$ and $\mathbf{c}$. The field-induced destabilization of the ferromagnetic state is also anisotropic: the anomaly at the Curie temperature $T_C$ disappears in fields higher than $\gtrsim1$~T for $\mathbf{H}\parallel\mathbf{a}$ and in fields higher than $\gtrsim20$~T for $\mathbf{H}\parallel\mathbf{b},\mathbf{c}$. At temperatures below 2~K, we observe quantum oscillations in fields larger than 50~T applied along $\mathbf{b}$, which support the presence of a two-dimensional Fermi surface similar to that previously observed at low fields.

cond-mat.str-el↗

arXiv2025

Boosted magnetic fluctuations at the onset of superconductivity in UTe$_2$ beyond 40 T

Several unconventional superconducting phases have been discovered close to a metamagnetic transition in the heavy-fermion compound UTe$_2$. Although suspected to be of magnetic nature, the mechanisms stabilizing these superconducting phases remain mysterious. Here, we present electrical-resistivity measurements on UTe$_2$, with a current $\mathbf{I}\parallel\mathbf{a}$ and under pulsed magnetic fields up to 60~T rotating in the ($\mathbf{b}$,$\mathbf{c}$) plane. We find that the maximum of the Fermi-liquid coefficient $A$ at the metamagnetic transition is enhanced under magnetic fields tilted by $30-40~^\circ$ from $\mathbf{b}$ to $\mathbf{c}$. The enhancement of $A$ coincides with the stabilization of superconductivity in the polarized paramagnetic regime beyond the metamagnetic field $\mu_0H_m\gtrsim40$~T. It is the signature of a boosted quantum-critical magnetic-fluctuation mode probably in play for the mechanism of this superconducting phase. This result appeals for descriptions of the interplay between magnetic-field-induced superconductivity and quantum critical magnetic properties.

cond-mat.str-el↗

arXiv2024

Metamagnetism in the high-pressure tetragonal phase of UTe$_2$

A structural orthorhombic-to-tetragonal phase transition was recently discovered in the heavy-fermion compound UTe$_2$ at a pressure $p^*\simeq3-8$~GPa [Honda \textit{et al.}, J. Phys. Soc. Jpn. \textbf{92}, 044702 (2023); Huston \textit{et al.}, Phys. Rev. Mat. \textbf{6}, 114801 (2022)]. In the high-pressure tetragonal phase, a phase transition at $T_x=235$~K and a superconducting transition at $T_{sc}=2$~K have been revealed. In this work, we present an electrical-resistivity study of UTe$_2$ in pulsed magnetic fields up to $\mu_0H=58$~T combined with pressures up to $p$ = 6 GPa. The field was applied in a direction tilted by 30~$^\circ$~from \textbf{b} to \textbf{c} in the orthogonal structure, which is identified as the direction \textbf{c} of the tetragonal structure. In the tetragonal phase, the presence of superconductivity is confirmed and signatures of metamagnetic transitions are observed at the fields $\mu_0H_{x1}=24$~T and $\mu_0H_{x2}=34$~T and temperatures smaller than $T_x$. We discuss the effects of uniaxial pressure and we propose that a magnetic ordering drives the transition at $T_x$.

cond-mat.str-el↗

arXiv2023

Incommensurate antiferromagnetism in UTe2 under pressure

The discovery of multiple superconducting phases in UTe2 boosted research on correlated-electron physics. This heavy-fermion paramagnet was rapidly identified as a reference compound to study the interplay between magnetism and unconventional superconductivity with multiple degrees of freedom. The proximity to a ferromagnetic quantum phase transition was initially proposed as a driving force to triplet-pairing superconductivity. However, we find here that long-range incommensurate antiferromagnetic order is established under pressure. The propagation vector km = (0.07,0.33,1) of the antiferromagnetic phase is close to a wavevector where antiferromagnetic fluctuations have previously been observed at ambient pressure. These elements support that UTe2 is a nearly-antiferromagnet at ambient pressure. Our work appeals for theories modelling the evolution of the magnetic interactions and electronic properties, driving a correlated paramagnetic regime at ambient pressure to a long-range antiferromagnetic order under pressure. A deeper understanding of itinerant-f-electrons magnetism in UTe2 will be a key for describing its unconventional superconducting phases.

cond-mat.str-el↗

arXiv2022

Anisotropic signatures of the electronic correlations in the electrical resistivity of UTe$_2$

Multiple unconventional superconducting phases are suspected to be driven by magnetic fluctuations in the heavy-fermion paramagnet UTe$_2$, and a challenge is to identify the signatures of the electronic correlations, including the magnetic fluctuations, in the bulk physical quantities. Here, we investigate thoroughly the anisotropy of the electrical resistivity of UTe$_2$ under intense magnetic fields up to 70~T, for different electrical-current and magnetic-field configurations. Two characteristic temperatures and an anisotropic low-temperature Fermi-liquid-like coefficient $A$, controlled by the electronic correlations, are extracted. Their critical behavior near the metamagnetic transition induced at $\mu_0H_m\simeq35$~T for $\mathbf{H}\parallel\mathbf{b}$ is characterized. Anisotropic scattering processes are evidenced and magnetic fluctuations are proposed to contribute, via a Kondo hybridization, to the electrical resistivity. Our work appeals for a microscopic modeling of the anisotropic contributions to the electrical resistivity as a milestone for understanding magnetically-mediated superconductivity in UTe$_2$.

cond-mat.str-el↗