Electrostatically Induced Superconductivity at the Surface of WS2

• Published in: Nano letters
• Main Authors: Jo, Sanghyun, Costanzo, Davide, Berger, Helmuth, Morpurgo, Alberto F
• Format: Journal Article
• Language: English
• Published: American Chemical Society 11.02.2015
• Subjects: superconductivity; ionic liquid gating; transition metal dichalcogenides; potential fluctuation, BKT transition; WS2
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl504314c

We investigate transport through ionic liquid gated field effect transistors (FETs) based on exfoliated crystals of semiconducting WS2. Upon electron accumulation, at surface densities close to, or just larger than, 1014 cm–2, transport exhibits metallic behavior with the surface resistivity decreasing pronouncedly upon cooling. A detailed characterization as a function of temperature and magnetic field clearly shows the occurrence of a gate-induced superconducting transition below a critical temperature T c ≈ 4 K, a finding that represents the first demonstration of superconductivity in tungsten-based semiconducting transition metal dichalcogenides. We investigate the nature of superconductivity and find significant inhomogeneity, originating from the local detaching of the frozen ionic liquid from the WS2 surface. Despite the inhomogeneity, we find that in all cases where a fully developed zero resistance state is observed, different properties of the devices exhibit a behavior characteristic of a Berezinskii–Kosterlitz–Thouless transition, as it could be expected in view of the two-dimensional nature of the electrostatically accumulated electron system.