The density and disorder tuned superconductor-metal transition in two dimensions

TL;DR

This study investigates the superconductor-metal transition in a 2D oxide interface, revealing how carrier density and disorder influence the emergence of pseudogap states and phase coherence, advancing understanding of 2D superconductivity.

Contribution

It introduces dual electrostatic gating to independently control carrier density and disorder, providing new insights into the phase diagram and transition mechanisms in 2D superconductors.

Findings

Pseudogap corresponds to precursor pairing.

Long-range phase coherence forms a 2D superconducting dome.

Transitions driven by phase fluctuations of Josephson puddles.

Abstract

Quantum ground states which arise at atomically controlled oxide interfaces provide an opportunity to address key questions in condensed matter physics, including the nature of two-dimensional (2D) metallic behaviour often observed adjacent to superconductivity. At the superconducting LaAlO3/SrTiO3 interface, a metallic ground state emerges upon the collapse of superconductivity with field-effect gating. Strikingly, such metallicity is accompanied with a pseudogap. Here, we utilize independent control of carrier density and disorder of the interfacial superconductor using dual electrostatic gates, which enables the comprehensive examination of the electronic phase diagram approaching zero temperature. We find that the pseudogap corresponds to precursor pairing, and the onset of long-range phase coherence forms a 2D superconducting dome as a function of the dual gate voltages. The gate-tuned superconductor-metal transitions are driven by macroscopic phase fluctuations of Josephson coupled superconducting puddles.