Strong optical response and valley-dependent Faraday rotation in monolayer Pt2HgSe3

In this article, we theoretically investigate the Faraday rotation in monolayer Pt2HgSe3. Materials in the jacutingaite family undergo topological phase transitions (TPTs), i.e., from a topologically nontrivial phase to a semimetallic phase and further to the normal insulating phase when exposed to electric fields and off-resonance, high-frequency, and high-intensity laser irradiation. We investigate the rich tapestry of topological phases in this unique material in the presence of an appropriate choice of off-resonance circularly polarized laser fields and staggered sublattice potentials. The interplay of these stimuli with large spin–orbit coupling, due to the buckled structure of jacutingaite materials, results in the emergence of quantum spin Hall insulator, valley-spin-polarized metal, spin-polarized metal, photo-induced quantum Hall insulator, anomalous quantum Hall insulator and band insulator phases. By using the Kubo formula, we calculate the spin-valley resolved longitudinal and Hall conductivities as a function of photon energies showing that the conductivities exhibit a strong topological state dependence. Furthermore, we calculate the Faraday rotation in jacutingaite in distinct topological phases. Remarkably, even in the absence of an external magnetic field, the breaking of time-reversal symmetry (TRS) in irradiated monolayer jacutingaite generates substantial spin and valley-polarized Faraday rotation of ≈±1.4∘. The Faraday rotation is a powerful and direct technique for measuring topological invariants and detecting topological phase transitions.