Low-energy bound states at interfaces between superconducting and block antiferromagnet regions in KxFe{2-y}Se2

TL;DR

This study investigates the electronic states at interfaces between superconducting and antiferromagnetic regions in KxFe{2-y}Se2, revealing abundant in-gap bound states and proposing a method to distinguish pairing symmetries.

Contribution

It provides a microscopic analysis of low-energy states at phase-separated interfaces in KxFe{2-y}Se2, highlighting the presence of in-gap bound states and a way to identify pairing symmetry.

Findings

In-gap bound states are present near interfaces regardless of pairing symmetry.

Nonmagnetic scattering planes can distinguish between d- and s-wave pairing.

The study uses a five orbital Hubbard model for analysis.

Abstract

The high-Tc alkali doped iron selenide superconductors KxFe{2-y}Se2 have been recently shown to be intrinsically phase separated into Fe vacancy ordered block antiferromagnetic regions and superconducting regions at low temperatures. In this work, we use a microscopic five orbital Hubbard model to obtain the electronic low-energy states near the interfaces between block antiferromagnets and superconductors. It is found that abundant low-energy in-gap bound states exist near such interfaces irrespective of whether the superconductor has d- or s-wave pairing symmetry. By contrast, it is shown how nonmagnetic scattering planes can provide a natural means to distinguish between these two leading pairing instabilities of the KxFe{2-y}Se2 materials.