Enhanced superconductivity in atomically thin TaS2

TL;DR

This study demonstrates that thinning down 2H tantalum disulfide to the atomic scale enhances its superconducting critical temperature, challenging previous notions that reduced dimensionality weakens superconductivity.

Contribution

It provides experimental evidence and a theoretical model showing that reducing layer thickness can strengthen superconductivity in 2D materials.

Findings

Superconductivity persists in layers as thin as 3.5 nm.

Critical temperature increases from 0.5 K to 2.2 K with thinning.

Enhanced electron-phonon coupling explains the phenomenon.

Abstract

The ability to exfoliate layered materials down to the single layer limit has opened the opportunity to understand how a gradual reduction in dimensionality affects the properties of bulk materials. Here we use this top-down approach to address the problem of superconductivity in the two-dimensional limit. The transport properties of electronic devices based on 2H tantalum disulfide flakes of different thicknesses are presented. We observe that superconductivity persists down to the thinnest layer investigated (3.5 nm), and interestingly, we find a pronounced enhancement in the critical temperature from 0.5 K to 2.2 K as the layers are thinned down. In addition, we propose a tight-binding model, which allows us to attribute this phenomenon to an enhancement of the effective electron-phonon coupling constant. This work provides evidence that reducing dimensionality can strengthen superconductivity as opposed to the weakening effect that has been reported in other 2D materials so far.