Modulated Vortex Lattice in High Fields and Gap Nodes

TL;DR

This paper investigates how gap nodes in a quasi-two-dimensional d-wave superconductor affect the stability of FFLO-like vortex lattices under high magnetic fields, suggesting the gap node in CeCoIn5 aligns with the [100] direction.

Contribution

It provides a theoretical analysis of the impact of gap nodes on vortex lattice stability in high-field superconductors, incorporating experimental insights.

Findings

FFLO-like state is suppressed near nodal directions

Gap node in CeCoIn5 likely along [100]-direction

Strong influence of gap anisotropy on vortex phases

Abstract

The mean field vortex phase diagram of a quasi two dimensional superconductor with a nodal d-wave pairing and with strong Pauli spin depairing is examined in the parallel field case in order to examine an effect of gap nodes (or minima) on the stability of a FFLO-like vortex lattice. We find through a heuristic argument and a model calculation with a four-fold anisotropic Fermi velocity that the FFLO-like state is relatively suppressed as the field approaches a nodal direction. When taking account of a couple of experimental results altogether, the present result strongly suggests that a node or gap minimum of the pairing function of CeCoIn$_5$ is located along the [100]-direction.