Signatures of unconventional pairing in near-vortex electronic structure of LiFeAs

TL;DR

This paper investigates the electronic structure near vortices in LiFeAs to identify signatures of unconventional pairing, using theoretical calculations to distinguish different gap symmetries through local density of states measurements.

Contribution

The study provides a theoretical framework to differentiate conventional and unconventional pairing in LiFeAs via vortex electronic structure analysis.

Findings

LDOS near vortices varies with gap symmetry at energies close to the gap value

Local gap profiles differ between conventional and unconventional pairing

In-field STM can serve as a probe for gap structure in Fe-based superconductors

Abstract

A major question in Fe-based superconductors remains the structure of the pairing, in particular whether it is of unconventional nature. The electronic structure near vortices can serve as a platform for phase-sensitive measurements to answer this question. By solving Bogoliubov-de Gennes equations for LiFeAs, we calculate the energy-dependent local electronic structure near a vortex for different nodeless gap-structure possibilities. At low energies, the local density of states (LDOS) around a vortex is determined by the normal-state electronic structure. However, at energies closer to the gap value, the LDOS can distinguish an anisotropic from a conventional isotropic s-wave gap. We show within our self-consistent calculation that in addition, the local gap profile differs between a conventional and an unconventional pairing. We explain this through admixing of a secondary order parameter within Ginzburg-Landau theory. In-field scanning tunneling spectroscopy near vortices can therefore be used as a real-space probe of the gap structure.