A goal of research in topological insulators (TI) is to imbue them with magnetism. Doing this in the right way leads to a semiconductor that is nearly superconducting, through the quantum anomalous Hall effect (QAHE). The figure shows extreme quantization of the QAHE conductivity reaching σyx = 0.9998 e 2/ h. The zero-field longitudinal resistance is only ρxx = 0.00013 h / e . [C.-Z. Chang, et al., Nature Matl. 14, 473 (2015)]
Although we have observed the QAHE at very low temperatures, our recent paper in Nature [F. Katmis 2016] reports on the discovery of a method to increase the operating temperature of the TI Bi2Se3. Instead of doping the TI with magnetic atoms as shown above, a magnetic exchange field is induced in bilayer Bi2Se3/EuS. In another study, magnetic exchange was also observed in a similar bilayer structure of the topological “crystalline” insulator SnTe/EuS.
Curie temperatures for the magnetic topological insulator V-doped and Cr-doped Sb2Te3. The inset shows a vanishing resistivity at the Hall plateau.