Recent Advances of Bulk Photovoltaic Effect in Exotic Quantum Materials: Progress and Challenges

Bulk photovoltaic (BPV) effect is a second-order nonlinear optical process that converts a light field into direct electric current and has attracted tremendous interest for efficient power conversion applications. The conventional photocurrent generations based on a single p-n junctions are generally governed by the Shockley-Queisser limit and require well-controlled atomic structure and band alignment. The BPV effect could occur in a single material without complicated heterojunction fabrication. The generated open-circuit electric voltage can be even higher than the bandgap of the hosting material, and the energy conversion efficiency could overcome the Shockley-Queisser limit. Here, we review BPV generation mechanisms, including the intrinsic shift current and extrinsic ballistic current, and their coupling with various (electric, magnetic, and topological) order parameters. As for the material platforms, we review recent experimental and theoretical advances on BPV generation in quantum materials, including ferroelectric and piezoelectric materials, magnetic materials, and band topological materials. Then, we summarize how BPV magnitude can be enhanced by reducing the bandgap of semiconductors and introducing band inversion or crossing between valence and conduction band edges in topological systems. Finally, we discuss the challenges for further theoretical and experimental understanding and their practical applications.