The realization of a giant and continuously tunable second-order photocurrent is desired for many nonlinear optical (NLO) and optoelectronic applications, which remains a great challenge. Here, based on a two-band model, we propose a concept of the bulk electrophotovoltaic effect, that is, an out-of-plane external electric field ($E_{\mathrm{ext}}$) that can continuously tune in-plane shift current along with its sign flip in a heteronodal-line (HNL) system. While strong linear optical transition around the nodal loop may potentially generate giant shift current, an $E_{\mathrm{ext}}$ can effectively control the radius of the nodal loop, which can continuously modulate the shift-vector components inside and outside the nodal loop holding opposite signs. This concept has been demonstrated in the HNL $\mathrm{HSnN}/{\mathrm{MoS}}_2$ system using first-principles calculations. The $\mathrm{HSnN}/{\mathrm{MoS}}_2$ heterobilayer can not only produce a shift-current conductivity with magnitude that is one to two orders larger than other reported systems, but it can also realize a giant bulk electrophotovoltaic effect. Our finding opens new routes to create and manipulate NLO responses in 2D materials.

• Received 17 November 2022
• Revised 27 April 2023
• Accepted 30 May 2023

DOI:https://doi.org/10.1103/PhysRevLett.130.256902