Reversible electrochemical modulation of the superconducting transition temperature of LiTi2O4 ultrathin films by ionic liquid gating

We demonstrate in situ modulation of the superconducting transition temperature (Tc) of LiTi2O4 thin films by ionic liquid gating. 15 nm thick LiTi2O4 thin films grown on MgAl2O4 substrates with the pristine Tc of 11.5 K was patterned into electric double-layer transistor devices for gating using ionic liquid with or without Li+ ions. The Tc of the LiTi2O4 thin film was found to decrease with a negative gate voltage for gating with either pure ionic liquid or Li+ containing ionic liquid. On the other hand, the recovery of Tc is observed at a positive gate voltage only for gating with the Li+ containing ionic liquid. The present observation suggests the possibility of reversible electrochemical modulation of superconducting properties by lithiation and delithiation.