Van Hove features in BSCCO(2212) and effective parameters for Ni impurities inferred from STM spectra

TL;DR

This paper compares theoretical and experimental STM spectra around Ni impurities in BSCCO(2212), identifying van Hove features and extracting impurity parameters relevant for understanding local electronic effects.

Contribution

It provides a detailed quantitative analysis linking theoretical models with STM measurements, revealing impurity-induced local electronic structure changes.

Findings

Identification of a spin-split van Hove singularity at Ni sites

Evidence of order parameter suppression near Ni impurities

Extraction of impurity parameters for macroscopic response calculations

Abstract

We present a detailed quantitative comparison between theoretical calculations of the local density of states and recent experimental measurements of scanning tunneling spectra around Ni impurities in BSCCO(2212). A double-peak structure on the hole side of the spectrum at the Ni site is identified as the spin-split van Hove singularity in the band structure. The Ni atom induces local changes in hopping matrix elements comparable in size to the induced on-site spin-dependent potential. We find evidence from the measurements of order parameter suppression in the vicinity of the Ni impurity. These extracted impurity parameters can be of use in quantitative calculations of macroscopic response properties, such as the AC conductivity.