Microscopic mechanism of electric field-induced superconductivity suppression in metallic thin films

TL;DR

This paper provides a quantitative microscopic explanation for how external electric fields suppress superconductivity in metallic thin films, using Eliashberg's theory and considering electrostatics and Cooper pair effects.

Contribution

It introduces a detailed theoretical framework to predict electric field-induced superconductivity suppression in thin films, aligning with experimental data.

Findings

Electric field of about 10^8 V/m suppresses superconductivity in 10-30 nm films.

The model aligns with experimental observations of field-induced suppression.

Framework can be extended to ultrathin films for further investigation.

Abstract

Supercurrent field-effect transistors made from thin metallic films are a promising option for next-generation high-performance computation platforms. Despite extensive research, there is still no complete quantitative microscopic explanation for how an external DC electric field suppresses superconductivity in thin films. This study aims to provide a quantitative description of superconductivity as a function of film thickness based on Eliashberg's theory. The calculation considers the electrostatics of the electric field, its realistic penetration depth in the film, and its effect on the Cooper pair, which is described as a standard s-wave bound state according to BCS theory. The estimation suggests that an external electric field of approximately $10^8$ V/m is required to suppress superconductivity in 10-30-nm-thick films, which aligns with experimental observations. Ultimately, the study offers "materials by design" guidelines for suppressing supercurrent when an external electric field is applied to the film surface. Furthermore, the proposed framework can be easily extended to investigate the same effects for ultrathin films.