Monolayer tetragonal group IV binary carbides for nonvolatile photovoltaics and spintronics

Nonvolatile controllable spin and photovoltaic phenomena are promising for future low-power, multifunctional electronic devices. However, studies on these effects in two-dimensional monolayers composed of carbon group elements remain limited. Here, based on first-principles, we identify stable monolayer two-dimensional tetragonal group IV carbides, namely, 2D t-SiC, t-GeC, and t-SnC, as potential candidates for ferroelastic materials. Among them, 2D t-GeC and t-SnC exhibit quantum spin Hall effect and anisotropic edge states, while t-SiC is a semiconductor with moderate direct bandgap of 1.71 eV that can display anisotropic photoresponsivity. The coexistence of ferroelastic, topological, and photovoltaic properties makes these monolayers promising for nonvolatile spintronic and optoelectronic devices. Our findings provide platforms for further research and application of two-dimensional materials based on carbon group elements.