Tuning electronic phase in noncentrosymmetric quantum spin Hall insulators through physical stimuli.

In this work, the perturbation-induced phase transitions in noncentrosymmetric quantum spin Hall insulators (QSHIs) are analytically addressed. In particular, the dilute charged impurity, the electric field, and the Zeeman splitting field are considered within the tight-binding Hamiltonian model, Green's function approach, and the Born approximation. Following thesymmetry breaking in the PbBiI compound as a representative QSHI, the band gap becomes larger via the electric field, while the system transits to the semimetallic phase via the dilute charged impurities and Zeeman field, modifying the degenerate states in the electronic density of states. While the coexistence of electric field and impurities demonstrate that the system backs to its initial semiconducting phase, the combined Zeeman field and impurities do not alter the robust semimetallic phase.