| Summary: | 碩士 === 國立臺灣大學 === 應用物理研究所 === 107 === So far, the highly-discussed topological phase transitions in Chern insulators have mostly been induced by tuning an intrinsic material parameter such as the exchange coupling strength. But it is not a practical way to induce topological phase transitions in real applications. Here we show that the topological phase transitions can be induced by tuning the extrinsic degree of freedom, magnetization orientation, in a Chern insulaotr formed by a two-dimensional electron gas with Dresselhaus [001] spin-orbit coupling and an exchange coupling to a ferromagnetic overlayer. In an analytic way, we show that this system has a topologically trivial phase with in-plane magnetization but undergoes a topological phase transition when the magnetization is deviated from the in-plane direction. The analytic results are further confirmed by numerical nonequilibrium Green functions calculations. With the combination of this phase transition and spin-transfer torque, a novel transistor can be designed with this promising fusion of topology and spintronics. At last, we combine this Chern insulator with an s-wave superconductor, forming the chiral topological superconductor. It will have vital applications in topological quantum computation.
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