Shift Current Engineering in BiSb

The bulk photovoltaic effect (BPVE) in noncentrosymmetric materials is a captivating physical phenomenon with the potential for high-efficiency energy harvesting. It is characterized by topological quantities; thus, topological phases often lead to large BPVE, especially shift current. In this work, we study the shift current BPVE in bulk BiSb, which is an intrinsic topological insulator and experiences a Weyl semimetal phase transition under hydrostatic pressure. Based on the first-principles calculations, we find that shift current flows along y and z directions under linearly polarized light irradiation. A hydrostatic pressure induces band gap reduction in BiSb and subsequently a significantly enhanced shift current. Specifically, at a pressure of 5 GPa, the magnitude of the first dominant peak of shift current is four times larger than that in pristine BiSb. Additionally, the flowing direction of the photoconductivity can be reversed by performing an inversion symmetry operation on the system. Overall, this work achieves ways to tailor the shift current via hydrostatic pressure and inversion symmetry operation in an intrinsic topological insulator BiSb compound successfully.