Quantum anomalous Hall effect in ferromagnetic Ru iodide monolayer.

Based on the successful synthesis of transition metal halides, we use first-principles calculations to predict that RuI$_{\mathrm{3}}$ monolayer is an intrinsic ferromagnetic QAH insulator with a topologically nontrivial global band gap of 11 meV. The band structure of RuI$_{\mathrm{3}}$ monolayer shows a Dirac cone in the spin down channel, while the spin up channel is insulating. When the spin-orbit coupling is included, the Dirac cone opens a finite band gap. This topologically nontrivial band gap at the Fermi level is due to its crystal symmetry, thus the QAH effect is robust. Its Curie temperature, estimated to be \textasciitilde 360 K using Monte-Carlo simulation, is above room temperature and higher than most of two-dimensional ferromagnetic thin films. We also discuss the manipulation of its exchange energy and nontrivial band gap by applying in-plane strain. This work adds a new experimentally feasible member to the QAH insulator family, which is expected to have broad applications in nanoelectronics and spintronics. Detailed information can be found in https://arxiv.org/pdf/1609.08115.