Induced superconductivity in noncuprate layers of the Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ high-temperature superconductor: Modeling of scanning tunneling spectra

TL;DR

This paper models how superconducting coherence peaks in Bi2212 are transferred from cuprate layers to adjacent oxide layers, revealing the layer-to-layer induction of superconductivity using multiband calculations.

Contribution

It provides a detailed multiband theoretical analysis of how superconductivity is induced in noncuprate layers of Bi2212, including symmetry and selection rules.

Findings

Superconducting pairing is induced across layers in Bi2212.

Anomalous Green's function elements reveal layer-to-layer pairing transfer.

Selection rules determine the symmetry properties of induced superconductivity.

Abstract

We analyze how the coherence peaks observed in Scanning Tunneling Spectroscopy (STS) of cuprate high temperature superconductors are transferred from the cuprate layer to the oxide layers adjacent to the STS microscope tip. For this purpose, we have carried out a realistic multiband calculation for the superconducting state of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) assuming a short range d-wave pairing interaction confined to the nearest-neighbor Cu $d_{x^2-y^2}$ orbitals. The resulting anomalous matrix elements of the Green's function allow us to monitor how pairing is then induced not only within the cuprate bilayer but also within and across other layers and sites. The symmetry properties of the various anomalous matrix elements and the related selection rules are delineated.