Electrical Modulation of Superconducting Critical Temperature in   Liquid-Gated Thin Niobium Films
  We demonstrate that the superconducting critical temperature (Tc) of thin niobium films can be electrically modulated in a liquid-gated geometry device. Tc can be suppressed and enhanced by applying positive and negative gate voltage, respectively, in a reversible manner within a range of about 0.1 K. At a fixed temperature below Tc, we observed that the superconducting critical current can be modulated by gate voltage. This result suggests a possibility of an electrically-controlled switching device operating at or above liquid helium temperature, where superconductivity can be turned on or off solely by the applied gate voltage. 
Jiman Choi, Pradheesh R., Hyungsang Kim, Hyunsik Im, Yonuk Chong,   Dong-Hun Chae
cond-mat.mes-hall