Tuning electronic properties of FeSe_(0.5)Te_(0.5) thin flakes using a solid ion conductor field-effect transistor

摘要

Using a field-effect transistor (FET) configuration with solid Li-ion conductor (SIC) as gate dielectric, we have successfully tuned carrier density in FeSe_(0.5)Te_(0.5) thin flakes, and the electronic phase diagram has been mapped out. It is found that electron doping controlled by SIC-FET leads to a suppression of the superconducting phase, and eventually gives rise to an insulating state in FeSe_(0.5)Te_(0.5). During the gating process, the (001) peak in x-ray diffraction patterns stays at the same position and no new diffraction peak emerges, indicating no evident Li+ ions intercalation into the FeSe_(0.5)Te_(0.5). It indicates that a systematic change of electronic properties in FeSe_(0.5)Te_(0.5) arises from the electrostatic doping induced by the accumulation of Li~+ ions at the interface between FeSe_(0.5)Te_(0.5) and solid ion conductor in the devices. It is striking that these findings are drastically different from the observation in FeSe thin flakes using the same SIC-FET, in which T_c is enhanced from 8 K to larger than 40 K, then the system goes into an insulating phase accompanied by structural transitions.