Strain-induced superconductor/insulator transition and field effect in a thin single crystal of molecular conductor

摘要

The strain in an organic field-effect channel was controlled using a pressure-sensitive organic superconductor κ-(BEDT-TTF)_2Cu[N(CN)_2]Br [BEDT-TTF=bis(ethylenedithio)tetrathia-fulvalene]. The difference in thermal properties between the channel and the substrate induced strain with cooling, resulting in a phase transition. An unshrinkable SiO_2/Si substrate was used to strain the subject material to the insulating state at low temperature, whereas a shrinkable polymer-based substrate allowed it to be a superconductor. The strain-induced insulating phase on SiO_2/Si is at the vicinity of the phase boundary with the superconducting phase, actualizing field-effect transistor behavior.