Two nonmagnetic impurities in the DSC and DDW state of the cuprate superconductors as a probe for the pseudogap

TL;DR

This study numerically investigates how two nonmagnetic impurities affect the local density of states in cuprate superconductors' DSC and DDW states, providing insights into the pseudogap's origin and testing different theoretical models.

Contribution

It offers a systematic analysis of impurity-induced LDOS modulations to distinguish between DSC and DDW states and assesses the potential scattering model in the context of cuprates.

Findings

Impurity interference patterns differ between DSC and DDW states.

LDOS modulations can identify the pseudogap's nature.

Results support using impurity studies to probe cuprate order parameters.

Abstract

The quantum interference between two nonmagnetic impurities is studied numerically in both the d-wave superconducting (DSC) and the d-density wave (DDW) state. In all calculations we include the tunnelling through excited states from the CuO$_2$ planes to the BiO layer probed by the STM tip. Compared to the single impurity case, a systematic study of the modulations in the two-impurity local density of states can distinguish between the DSC or DDW states. This is important if the origin of the pseudogap phase is caused by preformed pairs or DDW order. Furthermore, in the DSC state the study of the LDOS around two nonmagnetic impurities provide further tests for the potential scattering model versus more strongly correlated models.