Nematic order in the vicinity of a vortex in superconducting FeSe

TL;DR

This paper develops a phenomenological model describing how nematic order interacts with superconductivity near vortices in FeSe, predicting vortex core shapes and their dependence on bulk nematic order and magnetic field.

Contribution

It introduces a theoretical framework for nematic-superconductor interplay near vortices, explaining vortex core eccentricity behavior in FeSe.

Findings

Vortex cores become elliptical due to nematic order enhancement.

Eccentricity decay depends on bulk nematic order strength.

Results align with recent STM experiments on FeSe.

Abstract

We present a phenomenological theory of the interplay between nematic order and superconductivity in the vicinity of a vortex induced by an applied magnetic field. Nematic order can be strongly enhanced in the vortex core. As a result, the vortex cores become elliptical in shape. For the case where there is weak bulk nematic order at zero magnetic field, the field-induced eccentricity of the vortex core has a slow power-law decay away from the core. Conversely, if the nematic order is field-induced, then the eccentricity is confined to the vortex core. We discuss the relevance of our results to recent scanning tunnelling microscopy experiments on FeSe (Song et al., Science 332, 1410 (2011)).