Publication de Maxime Barbier

Ici vous trouverez l'article de Maxime Barbier :
"The archetypical heavy-fermion superconductor $\mathrm{Ce}{\mathrm{Cu}}_2{\mathrm{Si}}_2$ is known to present two distinct superconducting phases under pressure. In the low-pressure region, the superconductivity is mediated by spin fluctuations while the superconducting phase observed in the high-pressure region could be associated with a first-order valence transition (FOVT). However, the critical end point (CEP) of the FOVT was shown to be located at negative temperature and only a continuous valence change (crossover regime) was so far observed at 14 K, i.e., far above the optimal superconducting temperature $\left(T_c=2.3K\right)$. Here we present x-ray absorption measurements under pressure and applied magnetic field at the Ce $L_3$ edge at 2.7 K, i.e., close to the optimal $T_c$. It was expected that the applied magnetic field could shift the CEP to positive temperature with the possibility to observe a FOVT. Our data indicate the valence of Ce increases continuously (crossover regime) from 3.11 at ambient pressure up to 3.20 at 8.5 GPa likewise for any applied magnetic field up to 6 T."