Thermoelectric response as a tool to observe electrocaloric effect in a thin conducting ferroelectric SnSe flake

We experimentally investigate thermoelectric response of a 100~nm thick SnSe single crystal flake under the current-induced dc electric field. Thermoelectric response appears as a second-harmonic transverse voltage $V_{xy}^{2\omega }$, which reflects temperature gradient across the sample due to the Joule heating by harmonic ac excitation current $I_{ac}$. In addition to strongly non-monotonous dependence $V_{xy}^{2\omega }$, we observe that dc field direction controls the sign of the temperature gradient in the SnSe flake. We provide arguments, that electrocaloric effect is the mostly probable reason for the results obtained. Thus, our experiment can be understood as demonstration of the possibility to induce electrocaloric effect by in-plane electric field in conducting ferroelectric crystals and to detect it by thermoelectric response.