A novel route to a finite center-of-mass momentum pairing state; current driven FFLO state

TL;DR

This paper proposes a new method to realize FFLO states in superconductors with Fermi surface nesting by applying an external current, leading to a spontaneous finite pair-momentum that stabilizes the state.

Contribution

It introduces a novel route to achieve FFLO states via current-driven pair-momentum in nested Fermi surface superconductors, distinct from magnetic field methods.

Findings

FFLO state stabilized above a critical current depending on direction.

Spontaneous pair-momentum aligns to make total momentum perpendicular to nesting vector.

Experimental signatures of the current-driven FFLO state are suggested.

Abstract

The previously studied Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is stabilized by a magnetic field via the Zeeman coupling in spin-singlet superconductors. Here we suggest a novel route to achieve non-zero center-of-mass momentum pairing states in superconductors with Fermi surface nesting. We investigate two-dimensional superconductors under a uniform external current, which leads to a finite pair-momentum of ${\bf q}_{e}$. We find that an FFLO state with a spontaneous pair-momentum of ${\bf q}_{s}$ is stabilized above a certain critical current which depends on the direction of the external current. A finite ${\bf q}_s$ arises in order to make the total pair-momentum of ${\bf q}_t(={\bf q}_s + {\bf q}_e)$ perpendicular to the nesting vector, which lowers the free energy of the FFLO state, as compared to the superconducting and normal states. We also suggest experimental signatures of the FFLO state.