Investigation of strain-induced modulation on electronic and optical properties of monolayer of BSb

• Direct band gap of monolayer h-BSb is tunable by mechanical strain: increases with tensile and decreases with compressive. • Strain induces blue- and red-shifted optical peaks, highlighting strong strain-dependent optical tunability. • The DC Kerr effect shows a distinct, strain-modulated double-peak structure. • h-BSb exhibits lower-energy optical transitions and stronger mechanical deformation response than h-BP. This work presents a comprehensive theoretical investigation of the electronic and optical responses of monolayer honeycomb boron antimony (h-BSb) and hexagonal boron phosphide (h-BP) under various biaxial strain conditions, employing a tight-binding approach validated through DFT calculations. Our findings reveal that monolayer h-BSb possesses a direct band gap that can be effectively modulated through mechanical strain: tensile strain raises the band gap, whereas compressive strain decreases it. This strain-induced tunability manifests directly in the optical spectra, where prominent optical peaks exhibit significant redshifts under compressive strain and blueshifts under tensile conditions. The refractive index n ( ω ) demonstrates clear strain-dependent modulations, with the zero-frequency value increasing under compressive strain and decreasing under tensile deformation. Additionally, the DC Kerr effect displays a distinctive double-peak structure that shows high sensitivity to mechanical strain. Comparative analysis demonstrates that monolayer h-BSb exhibits lower-energy optical transitions and enhanced sensitivity to strain-induced peak displacement compared to h-BP. This superior performance stems from h-BSb’s small band gap and narrow interband separations at the points of high-symmetry in the Brillouin zone. These characteristics position h-BSb as a highly promising material for strain-engineered optoelectronic applications, particularly in infrared photodetectors and sensors.