Pressure effect on superconductivity in [formula omitted] studied by thermal expansion

Abstract

We present low-temperature thermal expansion measurements on the Sn-substituted heavy fermion superconductor CeCoIn 5 - x Sn x for 0 ⩽ x ⩽ 0.12 in which T c is rapidly suppressed from 2.3 ( x = 0 ) to 0.7 K ( x = 0.12 ). The analysis of the superconducting transition anomalies reveals a drastic change of the uniaxial pressure dependences of T c with Sn substitution. The hydrostatic pressure dependence of T c is positive for Sn concentrations x ⩽ 0.06 and changes sign at larger x . A first-order superconducting transition, caused by Pauli limiting in magnetic fields that suppress T c to below 0.7 K, is visible at x ⩽ 0.06 .