Topological Material-Based Spin Devices

Three-dimensional topological insulators have insulating bulk and gapless helical surface states. One of the most fascinating properties of the metallic surface states is the spin-momentum helical locking. The giant current-driven torques on the magnetic layer have been discovered in TI/ferromagnet bilayers originating from the spin-momentum helical locking, enabling the efficient magnetization switching with a low current density.$^{\mathrm{1}}$. We demonstrated the current-direction dependent on-off state in TIs-based spin valve devices for memory and logic applications.$^{\mathrm{2}}$\textbf{.} Further, we demonstrated the Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$ system will go from a topologically nontrivial state to a topologically trivial state when Bi atoms are replaced by lighter In atoms. Here, topologically trivial metal (Bi$_{\mathrm{x}}$In$_{\mathrm{y}})_{\mathrm{2}}$Se$_{\mathrm{3\thinspace }}$with high mobility also facilitates the realization of its application in multifunctional spintronic devices. .$^{\mathrm{1 }}$A. Mellnik, et al, Nature \textbf{511} (7510), 449 (2014). $^{\mathrm{2 }}$M. Zhang, et al, IEEE Electron Device Letters \textbf{37} (9), 1231 (2016).