Gate-tunable superconductivity at SrTiO3 surface realized by Al layer evaporation

TL;DR

This paper demonstrates a simple method to create a gate-tunable superconducting 2DEG on SrTiO3 by evaporating a thin Al layer, enabling easier study of low-dimensional superconductivity and many-body effects.

Contribution

It introduces a novel, simplified fabrication technique for oxide-based superconducting 2DEGs using Al evaporation, replacing more complex methods like PLD.

Findings

Superconducting 2DEG achieved by Al evaporation on SrTiO3.

Superconductivity tunable with gate voltage up to 360 mK.

Switching between superconducting and resistive states demonstrated.

Abstract

Electronic properties of low dimensional superconductors are determined by many-body-effects. This physics has been studied traditionally with superconducting thin films, and in recent times with two-dimensional electron gases (2DEGs) at oxide interfaces. In this work, we show that a superconducting 2DEG can be generated by simply evaporating a thin layer of metallic Al under ultra-high vacuum on a SrTiO3 crystal, whereby Al oxidizes into amorphous insulating alumina, doping the SrTiO3 surface with oxygen vacancies. The superconducting critical temperature of the resulting 2DEG is found to be tunable with a gate voltage with a maximum value of 360 mK. A gate-induced switching between superconducting and resistive states is demonstrated. Compared to conventionally-used pulsed-laser deposition (PLD), our work simplifies to a large extent the process of fabricating oxide-based superconducting 2DEGs. It will make such systems accessible to a broad range of experimental techniques useful to understand low-dimensional phase transitions and complex many-body-phenomena in electronic systems.