Superconducting BCS versus Fulde-Ferrell-Larkin-Ovchinnikov states of quasiparticles with spin dependent mass and their distinguishability

TL;DR

This paper develops a theoretical framework combining the observation of FFLO superconductivity and spin-dependent quasiparticle masses in CeCoIn_5, highlighting how spin-split masses and quasiparticle distinguishability extend FFLO detectability.

Contribution

It introduces a unified model incorporating spin-dependent masses and FFLO states in heavy fermion superconductors, emphasizing their impact on experimental observability.

Findings

Spin-split quasiparticle masses extend FFLO stability regime.

Quasiparticles in Cooper pairs become distinguishable under magnetic fields.

Theoretical framework unifies FFLO detection conditions with quasiparticle properties.

Abstract

The first observation of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconducting state and a subsequent detection of the spin-dependent effective masses of quasiparticles in the CeCoIn_5 heavy fermion system are combined into a single theoretical framework. The appearance of the spin-split masses extends essentially the regime of temperatures and applied magnetic fields, in which FFLO is observable and thus is claimed to be very important for the FFLO detectability. We also stress that the quasiparticles composing Cooper pair become distinguishable in the nonzero field. The analysis is performed within the Kondo-lattice limit of the finite-U Anderson-lattice model containing both the mass renormalization and real-space pairing within a single scheme.