All-armchair-edged <i>X</i>enes and optically controlled enhancement-mode transistor

Two-dimensional semiconductors are promising candidates for next-generation electronics due to their exceptional electrical, optical, and mechanical properties. However, developing enhancement-mode transistors compatible with current semiconductor technologies remains challenging. Here, we introduce a class of two-dimensional semiconductors—all-armchair-edged enes—the band gaps of which can be continuously tuned by adjusting the nanoribbon width or applying uniaxial strain. We demonstrate that a single circularly polarized light field induces different band gap variations for spin-up and spin-down electrons, enabling efficient spin filtering. Tensile strain enhances edge-state interactions, significantly increasing the band gap, especially in wider nanoribbons. Based on these findings, we propose an enhancement-mode field-effect transistor controlled solely by either left- or right-circularly polarized light and connected to topological insulator leads. The transistor’s threshold parameters, breakdown voltage, and output characteristics can be tailored by adjusting its channel width. Moreover, by adjusting the intensity and chirality of the light, we can selectively generate spin-up or spin-down currents. Using computer vision techniques, we propose a method to accurately reconstruct an all-armchair-edged lattice structure from scanning tunneling microscopy images.