Mechanisms of the in-plane magnetic anisotropy in superconducting NbSe2

TL;DR

This paper provides a unified theoretical framework explaining the in-plane magnetic anisotropies observed in two-dimensional superconducting NbSe2, linking symmetry, spin-orbit coupling, and tensor perturbations to various anisotropic phenomena.

Contribution

It introduces a comprehensive model that unifies different theoretical approaches to in-plane magnetic anisotropy in 2D superconductors, emphasizing the role of tensor perturbations and spin-orbit coupling.

Findings

Two-fold periodicity in transport requires tensor perturbation.

Six-fold variation of critical field arises from Rashba spin-orbit coupling.

Unified scheme clarifies differences between existing theoretical models.

Abstract

We present a unifying picture of the magnetic in-plane anisotropies of two-dimensional superconductors based on transition metal dichalcogenides. The symmetry considerations are first applied to constrain the form of the conductivity tensor. We hence conclude that the two-fold periodicity of transport distinct from the planar Hall related contributions requires a tensor perturbation. At the same time, the six-fold periodic variation of the critical field results from the Rashba spin-orbit coupling on a hexagonal lattice. We have considered the effect of a weak tensor perturbation on the critical field, gap function, and magneto-conductivity. The latter is studied using the time-dependent Ginzburg-Landau phenomenology. The common origin of the two-fold anisotropy in transport and thermodynamics properties is identified. The scheme constructed here is applied to describe the existing theoretical scenarios from a unified point of view. This allows us to single out the differences and similarities between the suggested approaches.