arXiv subjects

Benoit Fauqué

Publications and source records attributed to Benoit Fauqué.

5 recordsLinked to original sources

arXiv2021

Thermal conductivity of bulk In$_{2}$O$_{3}$ single crystals

The transparent semiconductor In$_{2}$O$_{3}$ is a technologically important material. It combines optical transparency in the visible frequency range and sizeable electric conductivity. We present a study of thermal conductivity of In$_{2}$O$_{3}$ crystals and find that around 20 K, it peaks to a value as high as 5,000 WK$^{-1}$m$^{-1}$, comparable to the peak thermal conductivity in silicon and exceeded only by a handful of insulators. The amplitude of the peak drastically decreases in presence of a type of disorder, which does not simply correlate with the density of mobile electrons. Annealing enhances the ceiling of the phonon mean free path. Samples with the highest thermal conductivity are those annealed in the presence of hydrogen. Above 100 K, thermal conductivity becomes sample independent. In this intrinsic regime, dominated by phonon-phonon scattering, the magnitude of thermal diffusivity, $D$ becomes comparable to many other oxides, and its temperature dependence evolves towards $T^{-1}$. The ratio of $D$ to the square of sound velocity yields a scattering time which obeys the expected scaling with the Planckian time.

cond-mat.mtrl-sci↗

arXiv2017

Superfluid density and carrier concentration across a superconducting dome: the case of SrTi$_{1-x}$Nb$_{x}$O$_{3}$

We present a study of the lower critical field, \hc1, of \STO as a function of carrier concentration with the aim of quantifying the superfluid density. At low carrier concentration (i.e. the underdoped side), superfluid density and the carrier concentration in the normal state are equal within experimental margin. A significant deviation between the two numbers starts at optimal doping and gradually increases with doping. The inverse of the penetration depth and the critical temperature follow parallel evolutions as in the case of cuprate superconductors. In the overdoped regime, the zero-temperature superfluid density becomes much lower than the normal-state carrier density before vanishing all together. We show that the density mismatch and the clean-to-dirty crossover are concomitant. Our results imply that the discrepancy between normal and superconducting densities is expected whenever the superconducting gap becomes small enough to put the system in the dirty limit. A quantitative test of the dirty BCS theory is not straightforward, due to he multiplicity of the bands in superconducting strontium titanate.

cond-mat.supr-con↗

arXiv2011

Nernst response of the Landau tubes in graphite across the quantum limit

We report on a study of the Nernst effect in graphite extended up to 45 T. The Nernst response sharply peaks each time a Landau tube is squeezed inside the thermally fuzzy Fermi surface and presents a temperature-independent fixed point whenever the tube flattens to a single ring. Beyond the quantum limit, the onset of the field-induced phase transition leads to a drastic drop in the Nernst response signaling the sudden vanishing of Landau tubes. The magnitude of this drop suggests the destruction of multiple Landau tubes possibly as a result of simultaneous nesting of the electron and hole pockets.

cond-mat.str-el↗

arXiv2008

Nature of the enigmatic pseudogap state: novel magnetic order in superconducting HgBa2CuO4+d

The nature of the enigmatic pseudogap region of the phase diagram is the most important and intriguing unsolved puzzle in the field of high transition-temperature (Tc) superconductivity. This region, the temperature range above Tc and below a characteristic temperature T*, is characterized by highly anomalous magnetic, charge transport, thermodynamic and optical properties. Associated with the pseudogap puzzle are open questions pertaining to the number of distinct phases and the presence of a quantum-critical point underneath the superconducting dome. Here we use polarized neutron diffraction to demonstrate for the model superconductor HgBa2CuO4+d (Hg1201) that T* marks the onset of an unusual magnetic order, and hence a novel state of matter with broken time-reversal symmetry. Together with prior results for YBa2Cu3O6+d (YBCO), this observation constitutes an essential and decisive demonstration of the universal existence of such a state. The new findings appear to rule out a large class of theories that regard T* as a crossover temperature rather than a phase transition temperature. Instead, they are consistent with a variant of previously proposed charge-current-loop order that involves apical oxygen orbitals, and with the notion that many of the unusual properties arise from the presence of a quantum-critical point.

cond-mat.supr-con↗

arXiv2006

Search for the existence of circulating currents in high-$T_c$ superconductors using the polarized neutron scattering technique

We review experimental attempts using polarized neutron scattering technique to reveal the existence in high temperature superconductors of a long-range ordered state characterized by the spontaneous appearance of current loops. We draw a particular attention to our recent results (B. Fauqué {\it et al.}, {\it Phys. Rev. Lett.} {\bf 96}, 197001 (2006)) that, up to now, can be explained only by the theory of circulating current proposed by C.M. Varma.

cond-mat.supr-con↗