Novel Chern insulators with half-metallic edge states

The central target of spintronics research is to achieve flexible control of highly efficient and spin-polarized electronic currents. Based on first-principles calculations and k·p models, we demonstrate that Cu2S/MnSe heterostructures are a novel type of Chern insulators with half-metallic chiral edge states and a very high Fermi velocity (0.87 × 106 m s−1). The full spin-polarization of the edge states is found to be robust against the tuning of the chemical potential. Unlike the mechanisms reported previously, this heterostructure has quadratic bands with a normal band order, that is, the p/d-like band is below the s-like band. Charge transfer between the Cu2S moiety and the substrate results in variation in the occupied bands, which together with spin–orbit coupling, triggers the appearance of the topological state in the system. These results imply that numerous ordinary semiconductors with normal band order may convert into Chern insulators with half-metallic chiral edge states through this mechanism, providing a strategy to find a rich variety of materials for dissipationless, 100% spin-polarized and high-speed spintronic devices. Non-magnetic semiconductors could be used to create spintronic devices with ultralow power consumptions, predicted by Chinese scientists. Spintronics is an emerging technology that processes information encoded in the spin on electrons. Recent years have also seen the development of topological insulators — materials that conduct a current across their surface with little loss. To merge these two concepts, Zhongqin Yang from Fudan University and her teammates simulated the properties of films of the semiconductor copper sulfide on the surface of manganese selenide. They showed that this creates a topological Chern insulator in which the low-loss surface states are fully spin polarized. Most existing spintronic materials are magnetic, but the team's simulation indicates that ordinary semiconductors could also be useful, opening more possibilities of materials that can realize completely spin polarized, high-speed spintronic devices. The built Cu2S/MnSe heterostructures belong to a novel type of Chern insulators, owning unique half-metallic chiral edge states and a very high Fermi velocity (0.87 × 106 m s−1). The full spin-polarization of the edge states is found to be robust against the tuning of chemical potential. This heterostructure has quadratic bands with normal band order, that is, the p/d-like band is below the s-like band. Charge transfer between the Cu2S and the substrate causes the variation of the occupied bands, which together with the spin–orbit coupling triggers the exotic topological state in the system.