Pressure induced FFLO instability in multi-band superconductors

TL;DR

This paper explores how pressure-induced hybridization in multi-band superconductors can lead to an FFLO phase, an inhomogeneous superconducting state, even without an external magnetic field.

Contribution

It demonstrates that increasing hybridization in a two-band BCS superconductor destabilizes the BCS state, favoring the emergence of an FFLO phase.

Findings

Hybridization controls the stability of superconducting phases.

An FFLO phase emerges at high hybridization levels.

The transition occurs at zero temperature.

Abstract

Multi-band systems as intermetallic and heavy fermion compounds have quasi-particles arising from different orbitals at their Fermi surface. Since these quasi-particles have different masses or densities, there is a natural mismatch of the Fermi wave-vectors associated with different orbitals. This makes these materials potential candidates to observe exotic superconducting phases as Sarma or FFLO phases, even in the absence of an external magnetic field. The distinct orbitals coexisting at the Fermi surface are generally hybridized and their degree of mixing can be controlled by external pressure. In this Communication we investigate the existence of an FFLO phase in a two-band BCS superconductor controlled by hybridization. At zero temperature, as hybridization (pressure) increases we find that the BCS state becomes unstable with respect to an inhomogeneous superconducting state characterized by a single wave-vector q.