Fluctuations superconductivity and giant negative magnetoresistance in a gate voltage tuned 2D electron liquid with strong spin-orbit impurity scattering

TL;DR

This paper develops a quantitative theory explaining the superconductor-insulator transition, giant negative magnetoresistance, and anomalous metallic behavior in a 2D electron liquid at oxide interfaces, emphasizing the role of spin-orbit scattering and quantum fluctuations.

Contribution

It introduces a novel phenomenological approach to include quantum fluctuations in the thermal fluctuations theory for 2D superconductors, aligning closely with experimental data.

Findings

Spin-orbit scattering enhances fluctuation interactions, increasing sheet resistance peaks.

Quantum fluctuations significantly influence the superconductor-insulator transition.

Heavy and light electron band mixing causes anomalous metallic behavior at low fields.

Abstract

We present a quantitative theory of the gate-voltage tuned superconductor-to-insulator transition (SIT) observed experimentally in the 2D electron liquid created in the (111) interface between crystalline SrTiO_3 and LaAlO_3 . Considering two fundamental opposing effects of Cooper-pair fluctuations; the critical conductivity enhancement, known as para-conductivity, and its suppression associated with the loss of unpaired electrons due to Cooper-pairs formation, we employ the standard thermal fluctuations theory, modified to include quantum fluctuations within a novel phenomenological approach. Relying on the quantitative agreement found between our theory and a large body of experimental sheet-resistance data, we conclude that spin-orbit scatterings, via significant enhancement of the interaction between fluctuations, strongly enhance the sheet resistance peak at high fields, and reveal anomalous metallic behavior at low fields, due to mixing of relatively heavy electron bands with a light electron band near a Lifshitz point.