Hidden sign-changing $s$-wave superconductivity in monolayer FeSe

TL;DR

This paper proposes a hidden sign-changing s-wave pairing symmetry in monolayer FeSe, supported by a tight-binding model and analysis of impurity-induced bound states, aligning with recent STM and ARPES data.

Contribution

It introduces a novel pairing function with hidden sign change that explains experimental observations in monolayer FeSe.

Findings

The proposed pairing function matches observed gap anisotropy.

Predicted impurity-induced bound states can be tested by STM.

Supports the existence of hidden sign-changing s-wave superconductivity.

Abstract

Combining the recent scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES) measurements, we construct a tight-binding model suitable for describing the band structure of monolayer FeSe grown on SrTiO$_{3}$. Then we propose a possible pairing function, which can well describe the gap anisotropy observed by ARPES and has a hidden sign-changing characteristic. At last, as a test of this pairing function we further study the nonmagnetic impurity-induced bound states, to be verified by future STM experiments.