Evidence for Superconducting Phase Coherence in the Metallic/Insulating Regime of the LaAlO3-SrTiO3 Interface Electron System

Abstract

A superconducting phase with an extremely low carrier density of the order of 10^13 cm^-2 is present at LaAlO3-SrTiO3 interfaces. If depleted from charge carriers by means of a gate field, this superconducting phase undergoes a transition into a metallic/insulating state that is still characterized by a gap in the spectral density of states. Measuring and analyzing the critical field of this gap, we provide evidence that macroscopically phase-coherent Cooper pairs are present in the metallic/insulating state. This is characterized by fluctuating vortex-antivortex pairs, and not by individual, immobile Cooper pairs. The measurements furthermore yield the carrier-density dependence of the superconducting coherence length of the two-dimensional system.

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Cited by in corpus (7)

• Physics of SrTiO${}_3$-based heterostructures and nanostructures: a review
• Anomalous metals -- failed superconductors
• When Superconductivity Crosses Over: From BCS to BEC
• Evidence of weak superconductivity at the room-temperature grown LaAlO${}_3$/SrTiO${}_3$ interface
• In-gap features in superconducting LaAlO${}_3$-SrTiO${}_3$ interfaces observed by tunneling spectroscopy
• Microwave properties of superconductors close to SIT
• Mesoscopic pairing without superconductivity