Optically induced spin Hall current in Janus transition metal dichalcogenides.(2024-2025)
Monolayer Janus transition-metal dichalcogenides (TMDCs), such as WSeTe, exhibit Rashba-type spin-orbit coupling (SOC) due to broken out-of-plane mirror symmetry. Here, we theoretically demonstrate that pure spin Hall currents can be generated under light irradiation based on a tight-binding model. Rashba-type SOC plays a crucial role in determining the spin polarization direction and enhancing the generation efficiency of pure spin Hall currents. Our findings establish Janus TMDCs as promising materials for next-generation optospintronic devices.
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Topological edge states induced by Zak’s phase in A3B monolayers.(2019)
In crystalline systems, charge polarization is related to the Zak phase determined by bulk band topology. Nontrivial charge polarization induces robust edge states accompanied by fractional charge. In the Su-Schrieffer-Heeger model, it is known that the strong modulation of electron hopping causes nontrivial charge polarization even in the presence of inversion symmetry. Here, we consider a biatomic honeycomb lattice to introduce such strong modulation, i.e., a A$_3$B sheet. By tuning the hopping ratio and on-site potential difference between the A and B atoms, we show that the topological phase transition characterized by the Zak phase occurs. Furthermore, we propose that C$_3$N and BC$_3$ are possible realistic materials on the basis of first-principles calculations. Both of them display topological edge states induced by the Zak phase without spin-orbital couplings and external fields, unlike conventional topological insulators.