Origin of Suppression of Proximity Induced Superconductivity in Bi/Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ Heterostructure

TL;DR

This study investigates why proximity-induced superconductivity is suppressed in Bi/Bi2212 heterostructures, revealing that electron transfer and underdoping at the interface hinder the effect, and proposes methods to mitigate this issue.

Contribution

The paper identifies the cause of suppressed proximity effect in Bi/Bi2212 heterostructures and suggests strategies to preserve superconductivity at the interface.

Findings

Electron transfer causes severe underdoping at the interface.

Absence of proximity effect is linked to interface doping.

Proposed methods could prevent loss of proximity effect.

Abstract

Mixing of topological states with superconductivity could result in topological superconductivity with the elusive Majorana fermions potentially applicable in fault-tolerant quantum computing. One possible candidate considered for realization of topological superconductivity is thin bismuth films on Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212). Here, we present angle-resolved and core-level photoemission spectroscopy studies of thin Bi films grown {\it in-situ} on as-grown Bi2212 that show the absence of proximity effect. We find that the electron transfer from the film to the substrate and the resulting severe underdoping of Bi2212 at the interface is a likely origin for the absence of proximity effect. We also propose a possible way of preventing a total loss of proximity effect in this system. Our results offer a better and more universal understanding of the film/cuprate interface and resolve many issues related to the proximity effect.