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

The strain in an organic field-effect channel was controlled using a pressure-sensitive organic superconductor κ- (BEDT-TTF)2 Cu [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 Si O2 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 Si O2 Si is at the vicinity of the phase boundary with the superconducting phase, actualizing field-effect transistor behavior.