Topological Phase Transitions Induced by Disorder in Magnetically Doped (Bi, Sb)2Te3 Thin Films

Physical Review B 102,20, 201405(R) (2020)

Topological Phase Transitions Induced by Disorder in Magnetically Doped (Bi, Sb)2Te3 Thin Films

Takuya Okugawa, Peizhe Tang, Angel Rubio, Dante M. Kennes

We study disorder induced topological phase transitions in magnetically doped (Bi, Sb)2Te3 thin films, by using large scale transport simulations of the conductance through a disordered region coupled to reservoirs in the quantum spin Hall regime. Besides the disorder strength, the rich phase diagram also strongly depends on the magnetic exchange field, the Fermi level, and the initial topological state in the undoped and clean limit of the films. In an initially trivial system at non-zero exchange field, varying the disorder strength can induce a sequence of transitions from a normal insulating, to a quantum anomalous Hall, then a spin-Chern insulating, and finally an Anderson insulating state. While for a system with topology initially, a similar sequence, but only starting from the quantum anomalous Hall state, can be induced. Varying the Fermi level we find a similarly rich phase diagram, including transitions from the quantum anomalous Hall to the spin-Chern insulating state via a state that behaves as a mixture of a quantum anomalous Hall and a metallic state, akin to recent experimental reports.

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We thank M. Brandbyge for fruitful discussions. This work was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) via RTG 1995 and Germanys Excellence Strategy - Cluster of Excellence Matter and Light for Quantum Computing (ML4Q) EXC 2004/1 - 390534769, by the European Research Council (ERC-2015-AdG-694097), Grupos Consolidados (IT1249-19) and the Flatiron Institute, a division of the Simons Foundation. Simulations were performed with computing resources granted by RWTH Aachen University under project rwth0601 and rwth0507. P.T. acknowledges the support from the Fundamental Research Funds for the Central Universities (ZG216S20A1) and the 111 Project (B17002). We acknowledge support from the Max Planck-New York City Center for Non-Equilibrium Quantum Phenomena. We acknowledge support of the Partner Group of the Max Planck Institute for the Structure and Dynamics of Matter at the School of Materials Science and Engineering, Beihang University, P.R China.

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