Topological properties and optical conductivities tuned by spin-orbit coupling and strain in kagome lattices

The spin-orbit coupling (SOC) effect is the dominant origin of the topological properties in a topological insulator which can be induced and enhanced through various methods. Here we theoretically study the effects of varying SOC on the topological properties of two-dimensional kagome lattice based on the tight-binding approximation. We find that the system can undergo a transition between two non-trivial topological states by tuning the SOC strength. In addition, the topological phase transition can be achieved with a weaker SOC under a uniform tensile strain, which suggests that strain engineering can be used to regulate topological states. Besides, the characteristics of optical spin Hall conductivity are also studied, which supplies an experimental determination to reveal the different topological states. Furthermore, we propose an external mechanical strain modulated spin-switch device, which can generate opposite spin currents under stretch and compressed strain. Our results indicate that with the combination of SOC and strain, kagome lattice materials have potential applications on tunable spintronics and optoelectronic devices.