A watchmaker's precision at high-pressure reveals CeCu2Si2 and CeAu2Si2 p-T phase diagrams

GIRIAT, G.; SCHEERER, G.W.; REN, Z.; PEDRAZZINI, P. ; LAPERTOT, G.; JACCARD, D.

Beijin

Conferencia; 26th International Conference of the AIRAPT; 2017

Nearly forty years after the discovery of the first heavy fermion (HF) superconductor, CeCu2Si2  [1], high-pressure (HP) investigations continue to provide information on the above and also enable the discovery of new Ce-based HF superconductors. Taking advantage of multiprobe HP setups we examined the resistivity, ac-magnetic susceptibility, ac-calorimetry and thermopower of CeCu2Si2 and CeAu2Si2 single crystals up to 27 GPa. We confirmed the existing p-T phase diagram of the former [2,3] based on bulk properties and found pressure-induced HF superconductivity in the latter. The ac-susceptibility study of CeCu2Si2 up to 5 GPa indicates that the superconducting (SC) transition signature observed from the magnetic field expulsion coincides with the specific heat jump and the zero resistivity. Below Tc, the diamagnetic signal is huge with a signal-to-noise ratio of 10^3 and corresponds to that expected for the sample volume. Thus the pressure dependence of Tc ( Tcmax≈2 K at 4 GPa), follows the bulk transition contrary to what is suggested by a previous report [4]. Furthermore, the broadening of the resistive SC  transition in the intermediate pressure range 2