Superconducting state of quasiparticles with spin dependent mass and their distinguishability for Cooper-pair state

TL;DR

This paper investigates how spin-dependent quasiparticle masses influence the stability of the FFLO superconducting phase and explores the quantum distinguishability of Cooper pairs under magnetic fields in strongly correlated systems.

Contribution

It demonstrates that spin-dependent masses extend the FFLO phase stability region and examines the quantum indistinguishability of Cooper pairs with spin-dependent mass effects.

Findings

Spin-dependent masses enlarge the FFLO stability regime.

Magnetic fields can break the antisymmetry of Cooper-pair wave functions.

Quantum distinguishability of pairs is affected by spin-dependent mass differences.

Abstract

Spin dependence of quasiparticle mass has been observed recently in CeCoIn5 and other systems. It emerges from strong electronic correlations in a magnetically polarized state and was predicted earlier. Additionally, the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)phase has also been discovered in CeCoIn5 and therefore, the question arises as to what extent these two basic phenomena are interconnected, as it appears in theory. Here we show that the appearance of the spin-split masses essentially extends the regime of temperature and applied magnetic field, in which FFLO state is stable, and thus, it is claimed to be very important for the phase detectability. Furthermore, in the situation when the value of the spin z-component \sigma differentiates masses of the particles, the fundamental question is to what extent the two mutually bound particles are indistinguishable quantum mechanically? By considering first the Cooper-pair state we show explicitly that the antisymmetry of the spin-pair wave function in the ground state may be broken when the magnetic field is applied.