A bifunctional spin detector made of quantum anomalous Hall insulator

Abstract

The spin selection of the topological boundary states (TBS) which are protected by the chiral-like symmetry in quantum anomalous Hall insulator (QAHI) can be used to construct a bifunctional spin detector (SD). Such device made of QAHIs in parallel with opposite chirality can divide an incoming spin-polarized current into two outgoing currents. The agreement between numerical and analytical calculation proves that the SD device functions as both spin filter and spin separator well in reflecting the spin polarization of source material from the ratio of two currents. The monotonic relation of spin polarization and current ratio suggests that using such kind of device, the spin polarization can be obtained directly. We also find that such device has a broad working energy region attributed by the TBS within the bulk gap. Combining with the result that the current ratio is barely dependent on the coupling between candidate materials and device, it is reasonable to apply this technique with a stable measuring accuracy. Furthermore, the features such as having simple geometry, being manipulated without external magnetic field, and the prospect of working at room temperature make this proposed device seem promising in developing future low-power-consumption spintronic device.