All-Optically Controlled Topological Transistor Based on Xenes

We theoretically propose an $X\mathrm{ene}$ ($X=\mathrm{Si}$, $\mathrm{Ge}$, or $\mathrm{Sn}$) transistor that can be operated with high and low threshold light parameters. The results reveal that a spin-dependent nonconductive path in the $X\mathrm{ene}$ superlattice can be formed by utilizing an off-resonant light-induced topological phase transition and the band mismatch between illuminated and unilluminated regions. This topological transistor can be switched between an on state with a $100\mathrm{%}$ spin-polarized weak current, an on state with a nonpolarized strong current, and an off state with a controllable breakdown voltage, just by adjusting the polarization state of circularly polarized light. With the assistance of an electric field, the $X\mathrm{ene}$ transistor can be operated at low light parameters, the threshold parameter of the transistor can be reduced to much lower than the spin-orbit coupling strength, and the breakdown voltage can be larger than the bulk band gap of the unilluminated $X\mathrm{ene}$. All the results indicate that the proposed $X\mathrm{ene}$ nanosystems are promising candidates for topological electronic devices.