Electric field control of superconducting fluctuations and quasiparticle interference at oxide interfaces

TL;DR

This study demonstrates how electric fields can tune superconducting fluctuations and quasiparticle interference at oxide interfaces, revealing complex conductivity behaviors beyond traditional models.

Contribution

It introduces a comprehensive model including quasiparticle interference and superconducting fluctuations to explain conductivity enhancements in oxide interfaces.

Findings

Conductivity increases are modulated by electrostatic fields.

Weak anti-localization and Maki-Thompson fluctuations explain the data.

Electron-phonon scattering influences decoherence times.

Abstract

We investigate tunable superconducting transitions in (111)$\mathrm{LaAlO}_3/\mathrm{KTaO}_3$ field-effect devices. Large increases in conductivity, associated with superconducting fluctuations, are observed far above the transition temperature. However, the standard Aslamazov-Larkin paraconductivity model significantly underestimates the effect observed here. We use a model that includes conductivity corrections from normal state quasiparticle interference together with all contributions from superconducting fluctuations evaluated at arbitrary temperatures and in the short-wavelength limit. Through analysis of the magnetoconductance and resistive transitions, we find that the large conductivity increase can be explained by a combination of weak anti-localization and Maki-Thompson superconducting fluctuations. Both contributions are enabled by a strong temperature dependence of the electron's decoherence time compatible with an electron-phonon scattering scenario. We find that conductivity corrections are modulated by the electrostatic field effect, that governs a competition between normal-state quasiparticle interference and superconducting fluctuations.