Enhanced superconductivity in atomically thin TaS2

The ability to exfoliate layered materials down to the single layer limit has presented 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 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 the dimensionality can strengthen superconductivity as opposed to the weakening effect that has been reported in other 2D materials so farFinancial support from the EU (ELFOS project and ERC Advanced Grant SPINMOL), the Spanish MINECO (Excellence Unit ‘‘María de Maeztu’’ MDM-2015-0538, Project Consolider-Ingenio in Molecular Nanoscience and projects MAT2011–25046 and MAT2014–57915-R, co-financed by FEDER), Dutch organization for Fundamental Research on Matter (FOM), NWO/OCW and the Comunidad Autonoma de Madrid (MAD2D-CM -S2013/MIT-3007- and NANOFRONTMAG-CM -S2013/MIT-2850) and the Generalitat Valenciana (Prometeo Program) are gratefully acknowledged. AC-G acknowledges financial support from the BBVA Foundation through the fellowship ‘I Convocatoria de Ayudas Fundacion BBVA a Investigadores, Innovadores y Creadores Culturales’ (‘Semiconductores ultradelgados: hacia la optoelectronica flexible’), from the MINECO (Ramón y Cajal 2014 program, RYC-2014-01406) and from the MICINN (MAT2014-58399-JIN