Model for Tunneling-mediated Impurity Resonances in Bilayer Cuprate Superconductors

TL;DR

This paper models how tunneling between layers in bilayer cuprate superconductors influences impurity resonances observed in local density of states, providing insights into their electronic properties.

Contribution

It introduces a theoretical model describing tunneling-mediated impurity resonances in bilayer cuprates, highlighting the dependence on tunneling strength, doping, and energy gap.

Findings

Resonant peaks appear when tunneling exceeds a critical value.

Resonant peak height oscillates and decreases with distance from impurity.

Resonance characteristics depend on doping, energy gap, and tunneling strength.

Abstract

We have studied tunneling-mediated local density of states (LDOS) of the surface layer of a bilayer cuprate, where a Zn impurity is located on the second Cu-O layer. When the tunneling strength between two Cu-O layers is larger than a critical value, the LDOS on the site just above the Zn impurity first exhibits a resonant peak near the Fermi surface. The larger the tunneling strength, the stronger the resonant peak. It is also shown that the height of the resonant peak oscillates decreasingly with the distance from the site just above the Zn impurity. The location of the resonant peak in the surface LDOS depends on doping, energy gap, and the tunneling strength, and has an opposite bias voltage to that on its nearest neighboring sites. The results could be tested by the STM experiments and be used to further understand the electronic properties of high temperature superconductors.