Interpretation of scanning tunneling quasiparticle interference and impurity states in cuprates

TL;DR

This paper combines first-principles Wannier functions with Bogoliubov-de Gennes equations to interpret STM data in cuprates, revealing the importance of Wannier function tails and providing a microscopic basis for quasiparticle interference patterns.

Contribution

It introduces a novel method integrating Wannier functions with BdG equations to accurately interpret STM images and quasiparticle interference in cuprate superconductors.

Findings

Successfully explains Zn impurity images on Bi2Sr2CaCu2O8 surface.

Shows quasiparticle interference patterns can be understood via Wannier function interference.

Achieves excellent agreement with experimental STM data.

Abstract

We apply a recently developed method combining first principles based Wannier functions with solutions to the Bogoliubov-de Gennes equations to the problem of interpreting STM data in cuprate superconductors. We show that the observed images of Zn on the surface of Bi$_2$Sr$_2$CaCu$_2$O$_8$ can only be understood by accounting for the tails of the Cu Wannier functions, which include significant weight on apical O sites in neighboring unit cells. This calculation thus puts earlier crude "filter" theories on a microscopic foundation and solves a long standing puzzle. We then study quasiparticle interference phenomena induced by out-of-plane weak potential scatterers, and show how patterns long observed in cuprates can be understood in terms of the interference of Wannier functions above the surface. Our results show excellent agreement with experiment and enable a better understanding of novel phenomena in the cuprates via STM imaging.