Dimensionality-confined superconductivity within SrNbO3-SrTiO3 heterostructures

TL;DR

This paper reports the discovery of superconductivity at 230 mK in SrNbO3-SrTiO3 heterostructures, where a low-carrier-density electron system in strained SrNbO3 exhibits quantum phenomena.

Contribution

It reveals a novel mechanism for 2DEG formation via charge transfer from a metallic SrNbO3 layer, distinct from insulator-insulator interfaces.

Findings

Superconductivity observed below 230 mK.

Electron system with record-low carrier density.

High mobility retained in a low-density quantum regime.

Abstract

Interfaces between transition-metal oxides are able to host two-dimensional electron gases (2DEGs) and exhibit exotic quantum phenomena. Here we report the observation of superconductivity below 230 mK for the heterostructure composed of SrNbO3 (SNO) and SrTiO3 (STO). Different from some other counterparts with two insulators, the metallic SNO provides a novel mechanism to form a quasi 2DEG by charge transfer from bulk towards interface under strain. The superconductivity, residing within the strained SNO layer near the interface, is contributed by an electron system with record-low carrier density. Notably, although embedded in a normal metallic layer with a carrier density 4 to 5 orders higher, the electron system is still uniquely well-protected to retain high mobility and lies deep in extreme quantum regime.