Impurity-Induced Bound Excitations on the Surface of Bi2Sr2CaCu2O8

TL;DR

This study uses scanning tunneling microscopy to investigate how atomic-scale impurities affect superconductivity in Bi2Sr2CaCu2O8, revealing localized low-energy excitations caused by non-magnetic defects.

Contribution

It provides direct experimental evidence of impurity-induced bound states at the surface of a high-temperature superconductor, confirming theoretical predictions for d-wave pairing symmetry.

Findings

Non-magnetic impurities create localized low-energy states.

Zero bias conductance peaks are observed near impurities.

Impurity states span energies within the superconducting gap.

Abstract

We have probed the effects of atomic-scale impurities on superconductivity in Bi_{2}Sr_{2}CaCu_{2}O_{8} by performing low-temperature tunneling spectroscopy measurements with a scanning tunneling microscope. Our results show that non-magnetic defect structures at the surface create localized low-energy excitations in their immediate vicinity. The impurity-induced excitations occur over a range of energies including the middle of the superconducting gap, at the Fermi level. Such a zero bias state is a predicted feature for strong non-magnetic scattering in a d-wave superconductor.