Strain-modulated bulk photovoltaic effect in negative piezoelectrics

The bulk photovoltaic effect (BPVE) is mostly studied in ferroelectric and piezoelectric systems with a sizable intrinsic and induced electric dipole moment. While most studies of BPVE are based on the conventional positive piezoelectric materials, their responses in negative piezoelectric systems remain rare. In this work, based on a minimum tight-binding model simulation, we adopt a chain model to illustrate how the BPVE evolves under mechanical deformation in negative piezoelectrics. We find that the BPVE responses are mainly governed by strain-induced shift vector variations. This is in contrast to the conventional positive piezoelectrics. Moreover, such a mechanism is further illustrated in realistic quasi-layered negative piezoelectrics, i.e., rhombohedral GeX (X = S, Se, Te), via density functional theory calculations. Our work provides in-depth insights into BPVE engineering in unconventional negative piezoelectrics.