Strain engineering of multi-interband optical transitions in β12-borophene

The optical conductivity of strained monolayer β12-borophene is investigated via the Kubo formula and the five-band tight-binding method. In our model, the hopping energy of electrons is modified by strain following the Harrison rule. We investigate the effect of these modifications on the electronic dispersion and optical conductivity. Our results indicate that inherent massless Dirac fermions become massive with tensile strain and that inherent triplet fermions are doubled with compressive strain. Moreover, the strain-induced longitudinal optical conductivity was found to show a redshift spectrum with both tensile and compressive strains, while a blueshift spectrum was appeared for the transverse/Hall optical conductivity. These results show that strain can tune both electronic properties of β12-borophene and relevant practical optoelectronic applications.