DQMP and GAP, Université de Genève , 24 quai Ernest Ansermet, CH-1211 Geneva, Switzerland.
Nano Lett. 2015 Feb 11;15(2):1197-202. doi: 10.1021/nl504314c. Epub 2015 Jan 26.
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, 10(14) 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 Tc ≈ 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.
我们研究了基于剥离 WS2 半导体晶体的离子液体门控场效应晶体管 (FET) 的输运特性。在电子积累过程中，当表面密度接近或略大于 10(14)cm(-2)时，输运表现出金属行为，表面电阻随冷却显著下降。作为温度和磁场函数的详细表征清楚地表明，在临界温度 Tc ≈ 4 K 以下发生了栅极诱导超导转变，这一发现代表了在基于钨的半导体过渡金属二卤化物中首次观察到超导性。我们研究了超导的性质，并发现了显著的非均匀性，这源于冻结的离子液体与 WS2 表面的局部分离。尽管存在非均匀性，但我们发现，在观察到完全发展的零电阻状态的所有情况下，器件的不同特性表现出 Berezinskii-Kosterlitz-Thouless 转变的特征行为，这与静电积累电子系统的二维性质相一致。
