Strain controlled superconductivity in few-layer NbSe2

TL;DR

This paper demonstrates strain-induced superconductor-insulator transitions in few-layer NbSe2, enabling scalable tunnel barriers for quantum electronic devices by controlling superconductivity through strain.

Contribution

It reveals strain as a key control parameter for superconductor-insulator transitions in epitaxial NbSe2, facilitating the development of high-quality hetero-junction tunnel barriers.

Findings

Superconductor-insulator transition driven by strain.

Wafer-scale uniformity of epitaxial NbSe2.

Potential for scalable quantum device integration.

Abstract

The controlled tunability of superconductivity in low-dimensional materials may enable new quantum devices. Particularly in triplet or topological superconductors, tunneling devices such as Josephson junctions etc. can demonstrate exotic functionalities. The tunnel barrier, an insulating or normal material layer separating two superconductors, is a key component for the junctions. Thin layers of NbSe2 have been shown as a superconductor with strong spin orbit coupling, which can give rise to topological superconductivity if driven by a large magnetic exchange field. Here we demonstrate the superconductor-insulator transitions in epitaxially grown few-layer NbSe2 with wafer-scale uniformity on insulating substrates. We provide the electrical transport, Raman spectroscopy, cross-sectional transmission electron microscopy, and X-ray diffraction characterizations of the insulating phase. We show that the superconductor-insulator transition is driven by strain, which also causes characteristic energy shifts of the Raman modes. Our observation paves the way for high quality hetero-junction tunnel barriers to be seamlessly built into epitaxial NbSe2 itself, thereby enabling highly scalable tunneling devices for superconductor-based quantum electronics.