Vortex tilt modulus in Fulde-Ferrell-Larkin-Ovchinnikov state

TL;DR

This paper theoretically investigates how the vortex tilt modulus in the FFLO state reflects the spatial structure, revealing a reduction in tilt response linked to the FFLO transition, especially in anisotropic materials like CeCoIn5.

Contribution

It provides a theoretical analysis of vortex tilt response in the FFLO state, connecting the reduction of tilt modulus to the spatial structure and experimental ultrasound observations.

Findings

Vortex tilt modulus decreases in the FFLO state with nodal planes.

Reduction of tilt modulus is more significant in anisotropic systems.

This reduction may explain ultrasound velocity decrease in CeCoIn5.

Abstract

Vortex tilt response in Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) vortex lattice is theoretically examined as a probe reflecting the spatial structure of this state. In the FFLO state with nodal planes perpendicular to the magnetic field in a quasi 2D material under a parallel field, the tilt modulus E_{2} {\it of the nodal planes} decreases as the paramagnetic effect is effectively enhanced, and this reduction of E_{2} in turn reduces the vortex tilt modulus. This reduction of vortex tilt modulus, more remarkable in more anisotropic systems, accompanying the FFLO transition may be an origin of the monotonous reduction of sound velocity detected upon cooling in a ultrasound measurement for CeCoIn5.