Shift current in the ferroelectric semiconductor SbSI

A spontaneous photocurrent, termed a shift current, can flow in noncentrosymmetric bulk crystals due to the topological nature of the constituting electronic bands. A shift current with a less dissipative character may have remarkable advantages over the conventional drift photocurrent driven by a built-in potential or external electric field. We revisit the generation and transport of the shift current in a prototypical ferroelectric semiconductor SbSI near its band-gap energy. It is revealed that a switchable shift current is steadily generated by photoexcitation down to low temperatures, appears over a distance of millimeter range in a highly insulating bulk without noticeable decay, and largely exceeds the polarization charge in the sample, reflecting its Berry phase origin.