Theory of pairing symmetry in Fulde-Ferrell-Larkin-Ovchinnikov vortex state and vortex lattice

TL;DR

This paper analyzes the pairing symmetry in FFLO vortex states, revealing how even and odd frequency pairings manifest at different points and under varying Zeeman splitting, providing insights into the electronic structure.

Contribution

It offers an analytical explanation of pairing symmetries in FFLO vortex states and their relation to the electronic density of states, highlighting the emergence of odd and even frequency pairings.

Findings

At the intersection of FFLO nodal plane and vortex line, only even frequency pairing exists with negligible Zeeman splitting.

Increasing Zeeman splitting induces odd frequency pairing at the intersection point.

In vortex lattices, odd frequency pairing is found at vortex cores, while even frequency pairing occurs at vortex line midpoints.

Abstract

We investigate pairing symmetry in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) vortex state and vortex lattice, and explain the electronic structure in these states in terms of pairing symmetry. We show analytically that at the intersection point of FFLO nodal plane and vortex line, only even frequency pairing is present if the Zeeman splitting is negligibly small. With increasing Zeeman splitting, odd frequency pairing emerges there. This makes it possible to interpret the gap structure of the density of states at the intersection point as a manifestation of the even frequency pairing. In the vortex lattice, we find that only odd frequency pairing is present at the core centers, while at the midpoint of the vortex lines, only even frequency pairing exists. Thus, the odd and even frequency pairings also form the lattice in the vortex lattice state.