Control of Organic Superconducting Field-Effect Transistor by Cooling Rate

A new superconducting field-effect transistor (FET) in the vicinity of bandwidth-controlled Mott transition was developed using molecular strongly correlated system κ-(BEDT-TTF)2Cu[N(CN)2]Br [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene] laminated on CaF2 substrate. This device exhibited significant cooling-rate dependence of resistance below about 80 K, associated with glass transition of terminal ethylene group of BEDT-TTF molecule, where more rapid cooling through glass transition temperature leads to the decrease in bandwidth. We demonstrated that the FET properties such as ON/OFF ratio and polarity can be controlled by utilizing cooling rate. Our result may give a novel insight into the design of molecule-based functional devices.