Switchable out-of-plane shift current in ferroelectric two-dimensional material CuInP2S6

Polar materials are interesting platforms for fundamental research because they exhibit the spontaneous electric polarization (SEP) and the shift current photovoltaic effect, both originating from the inherent Berry connection. Owing to the electrical controllability, these phenomena are often studied in ferroelectric materials. Recently, the SEP and the shift current are enthusiastically studied in two-dimensional materials, but an electrical control has not been realized. In this study, we observed an out-of-plane shift current and demonstrated its electrical control at room temperature in a ferroelectric two-dimensional material CuInP2S6, by utilizing a multilayer graphene as a transparent electrode. The shift current origin was confirmed by an analysis of the excitation power dependence. Our results are an important step in the study of the Berry connection physics as well as put forward a device concept to utilize out-of-plane shift current photovoltaic effect for optoelectronic devices.