Switching ferroelectricity in SnSe across diffusionless martensitic phase transition

Abstract

We experimentally investigate transport properties of a hybrid structure, which consists of a thin single crystal SnSe flake on a top of 5~$μ$m spaced Au leads. The structure initially is in highly-conductive state, while it can be switched to low-conductive one at high currents due to the Joule heating of the sample, which should be identified as $α$-$Pnma$ -- $β$-$Cmcm$ diffusionless martensitic phase transition in SnSe. For highly-conductive state, there is significant hysteresis in $dI/dV(V)$ curves at low biases, so the sample conductance depends on the sign of the applied bias change. This hysteretic behavior reflects slow relaxation due to additional polarization current in the ferroelectric SnSe phase, which we confirm by direct measurement of time-dependent relaxation curves. In contrast, we observe no noticeable relaxation or low-bias hysteresis for the quenched $β$-$Cmcm$ low-conductive phase. Thus, ferroelectric behavior can be switched on or off in transport through hybrid SnSe structure by controllable $α$-$Pnma$ -- $β$-$Cmcm$ phase transition. This result can also be important for nonvolatile memory development, e.g. phase change memory for neuromorphic computations or other applications in artificial intelligence and modern electronics.