Direct Numerical Demonstration of Sign-preserving Quasiparticle Interference via Impurity inside Vortex Core in Unconventional Superconductors

TL;DR

This study uses large-scale numerical simulations to show that impurities inside vortex cores in unconventional superconductors enhance sign-preserving quasiparticle interference patterns, aligning with experimental observations.

Contribution

It provides the first direct numerical demonstration that impurities within vortex cores enhance sign-preserving QPI peaks, clarifying the role of Andreev bound states.

Findings

Vortex cores alone do not cause QPI patterns.

Impurities inside vortex cores enhance sign-preserving QPI peaks.

The origin of enhancement is due to impurity-distorted Andreev bound states.

Abstract

We perform large-scale numerical calculations self-consistently solving the Bogoliubov-de Gennes (BdG) equations in the magnetic field together with random impurities to directly demonstrate the typical quasi-particle interference (QPI) in the presence of vortices as observed by scanning tunneling microscopy/spectroscopy experiments in unconventional superconductors. The calculations reveal that vortex itself never works as a scatter causing the QPI pattern but vortex core containing impurity brings about the enhancement of the sign-preserving QPI peaks. Its origin is Andreev bound-states distorted by impurity, and all the measurement findings are consistently explained by the scenario based on the numerical results.