High-precision realization of robust quantum anomalous Hall state in a hard ferromagnetic topological insulator

TL;DR

This paper reports the experimental realization of a robust quantum anomalous Hall state in V-doped topological insulator films, demonstrating dissipationless edge conduction at very low temperatures, with potential for electronic applications.

Contribution

It presents the first observation of a high-precision, robust QAH state in a hard ferromagnetic topological insulator with high coercivity and Curie temperature.

Findings

Hall conductance close to e^2/h

Zero-field longitudinal resistance ~3.35 ohms

Hall angle nearly 90 degrees at 25 mK

Abstract

The discovery of the quantum Hall (QH) effect led to the realization of a topological electronic state with dissipationless currents circulating in one direction along the edge of a two dimensional electron layer under a strong magnetic field. The quantum anomalous Hall (QAH) effect shares a similar physical phenomenon as the QH effect, whereas its physical origin relies on the intrinsic spin-orbit coupling and ferromagnetism.Here we report the experimental observation of the QAH state in V-doped (Bi,Sb)2Te3 films with the zero-field longitudinal resistance down to 0.00013+-0.00007h/e2 (~3.35+-1.76 ohm), Hall conductance reaching 0.9998+-0.0006e2/h and the Hall angle becoming as high as 89.993+-0.004degree at T=25mK. Further advantage of this system comes from the fact that it is a hard ferromagnet with a large coercive field (Hc>1.0T) and a relative high Curie temperature. This realization of robust QAH state in hard FMTIs is a major step towards dissipationless electronic applications without external fields.