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.
@article{arxiv.1604.05656,
title = {Enhanced superconductivity in atomically thin TaS2},
author = {Efrén Navarro-Moratalla and Joshua O. Island and Samuel Mañas-Valero and Elena Pinilla-Cienfuegos and Andres Castellanos-Gomez and Jorge Quereda and Gabino Rubio-Bollinger and Luca Chirolli and Jose Angel Silva-Guillén and Nicolás Agraït and Gary A. Steele and Francisco Guinea and Herre S. J. van der Zant and Eugenio Coronado},
journal= {arXiv preprint arXiv:1604.05656},
year = {2016}
}