Anisotropy of the upper critical field in URu 2Si 2 and FFLO state in antiferromagnetic superconductors

Abstract

Experimental data of the upper critical field of the heavy-fermion superconductor URu 2Si 2 are analysed, in the clean limit, taking account of both orbital and Pauli limits. A discussion on the possible existence of a non-uniform superconducting state expected in clean Pauli-limited superconductors (FFLO state) follows. We also present calculations determining the influence of an AF ground state on the existence of such a non-uniform superconducting state.