Topological spintronics and Majorana fermions

Spin-orbit interaction has offered a versatile platform in the study of novel physical phenomena in condensed matters. It enables charge-to-spin conversion for implementing functional spintronic devices, and can even change the band topology when it is strong enough, giving rise to exotic quantum states of matters such as topological insulators (TIs). Here, we demonstrate functional topological spintronic devices employing multiple TI-based material structures. First, we achieved current-driven magnetization switching in TI/ferrimagnet heterostructures at room temperature. A low switching current density and a fast switching speed is demonstrated in this system, due to the highly efficient topological surface states and the fast spin dynamics near compensation point in ferrimagnets. Besides, the magnetization switching can be even realized without the assist of external magnetic field in a magnetic TI/antiferromagnet system, making it a promising candidate for applicable spintronic memory devices. Finally, when interfacing a quantum anomalous Hall insulator TI with Nb, an s-wave superconductor, the signature of chiral Majorana edge modes is observed as the half-quantized plateaus of e²/2h in conductivity. The experimental evidence of Majorana Fermions holds promise for error-tolerant topological quantum computation robust against external local perturbations.