Two impurities in a d-wave superconductor:local density of states

TL;DR

This paper investigates how two impurities in a d-wave superconductor affect quasiparticle states and local density of states, proposing STM experiments to extract detailed electronic information.

Contribution

It introduces a detailed analysis of two-impurity interference effects on quasiparticle states and LDOS in d-wave superconductors, linking theory with STM measurement potential.

Findings

Impurity resonances split into even and odd parity states due to interference.

Highly localized, long-lived states can form depending on impurity configuration.

STM measurements can reveal Green's function details and distinguish impurity effects.

Abstract

We study the problem of two local potential scatterers in a d-wave superconductor, and show how quasiparticle bound state wave functions interfere. Each single-impurity electron and hole resonance energy is in general split in the presence of a second impurity into two, corresponding to one even parity and one odd parity state. We calculate the local density of states (LDOS), and argue that scanning tunneling microscopy (STM) measurements should be capable of extracting information about the Green's function in the pure system by a systematic study of 2-impurity configurations. In some configurations highly localized, long-lived states are predicted. We discuss the effects of realistic band structures, and how 2-impurity STM measurements could help distinguish between current explanations of LDOS impurity spectra in the BSCCO-2212 system.