Electrical Manipulation of Topological Phases in Quantum Anomalous Hall Insulator.

Quantum anomalous Hall phases arising from the inverted band topology in magnetically-doped topological insulators have emerged as an important subject of research for quantization at zero magnetic fields. Though necessary for practical implementation, sophisticated electrical control of molecular beam epitaxy grown quantum anomalous Hall matter have been stymied by growth and fabrication challenges. Here we demonstrate a novel procedure, employing a combination of thin film deposition and two-dimensional material stacking techniques, to create dualgated devices of the molecular beam epitaxy grown quantum anomalous Hall insulator, Cr-doped (Bi,Sb) 2 Te 3 . In these devices, we demonstrate orthogonal control over the field-induced charge density and electric displacement field. We present a thorough examination of material responses to tuning along each control axis, realizing magnetic property control along the former and a novel capability to manipulate the surface exchange gap along the latter. Through electrically addressing the exchange gap, the capabilities to either strengthen the quantum anomalous Hall state or suppress it entirely and drive a topological phase transition to a trivial state are demonstrated. The experimental result is explained using first principle theoretical calculations, and establishes a practical route for in-situ control of quantum anomalous Hall states and topology. This article is protected by copyright. All rights reserved.