Promising TMDC-like optical and excitonic properties of the TiBr2 2H monolayer

Abstract

The presented simulation protocol provides a solid foundation for exploring two-dimensional materials. Taking the TiBr₂ 2H monolayer as an example, this material displays promising TMDC-like optical and excitonic properties, making it an excellent candidate for optoelectronic and valleytronic applications. The direct band gap semiconductor (1.19 eV) is both structurally and thermodynamically stable, with spin–orbit coupling effects revealing a broken mirror symmetry in the K and K′ valleys of the band structure, as confirmed by opposite values of the Berry curvature. A direct and bright exciton ground state was found, with an exciton binding energy of 0.56 eV. The study also revealed an optical helicity selection rule, suggesting selectivity in the valley excitation by specific circular light polarizations.