The recently synthesized two-dimensional Janus material ${\mathrm{Bi}}_2{\mathrm{TeSe}}_2$ offers great potential for nonlinear quantum transport owing to its intrinsically noncentrosymmetric crystal structure. However, its inherent ${\mathcal{C}}_{3v}$ symmetry enforces a cancellation of the Berry curvature dipole (BCD), the key quantity underlying the nonlinear Hall effect. In this work, we demonstrate the controlled generation of a finite BCD through symmetry engineering. By applying uniaxial strain, either compressive or tensile, a finite BCD is induced in monolayer ${\mathrm{Bi}}_2{\mathrm{TeSe}}_2$ which can yield substantial values ($1–10\AA$) near the valence band maximum. Furthermore, our calculations reveal that the inherent inversion symmetry breaking generates a shift current with an intrinsic conductivity of $-1000\mu \mathrm{A}\AA /{\mathrm{V}}^2$ in the undoped case. Most strikingly, hole doping shifts the Fermi level into the valence band, producing a fivefold enhancement of the shift conductivity. This is evidenced by distinct peaks of $\pm 5000 \mu \mathrm{A}\AA /{\mathrm{V}}^2$ in the terahertz regime and at a midinfrared photon energy of 0.2 eV, demonstrating the significant impact of the Fermi energy. Thus, strain selectively modulates the nonlinear Hall effect, while doping drastically improves bulk photovoltaic performance. These approaches offer general strategies for designing Janus materials with tailored transport and optoelectronic properties.

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• Anomalous Hall effect
• Shift current
• Janus materials
• Density functional theory