Quasiparticle and excitonic properties of monolayer 1 T ′ WTe 2 within many-body perturbation theory

Among existing band structure predictions of the topological monolayer 1$T$`-WTe${}₂$, only a semi-empirical hybrid functional has been able to reproduce the gapped electronic structure observed by angle-resolved photoemission spectroscopy (ARPES). Here, the authors demonstrate that the electronic band structure can be obtained by updating the quasiparticle wave functions within many-body perturbation theory (MBPT). Moreover, Bethe-Salpeter equation (BSE) on top of the gapped band structure leads to negative exciton frequencies, suggesting a possible exciton instability consistent with experimental evidence.