Research Status Surface states of topological insulators (TIs) are expected to exhibit many valuable new electronic phenomena when a 'mass gap' is opened in their Dirac spectrum by ferromagnetism (FM). Such ferromagnetic topological insulators (FMTI) should exhibit phenomena including the Quantum Anomalous Hall Effect (QAHE), the Jackiw-Rebbi Solitons (JRS), and Emergent Axionic Electrodynamics. The QAHE has indeed been observed but, mysteriously, it is only detected at mK temperatures. FIGURE 3A. Intensity of tunneling conductance g(q,E) into the Dirac spectrum of surface-states of Cr0.08(Bi0.1Sb0.9)1.92Te3; the ferromagnetism opens a gap ΔFM~20meV around the Dirac point where the conductance reaches zero. B. Tunneling conductance at a single atomic location; again ΔFM~20meV where the conductance reaches zero. C. Typical spatial map of ΔFM(r) in Cr0.08(Bi0.1Sb0.9)1.92Te3. |
Research Plans a) In general, ferromagnets exhibit both FM domains and magnetic hysteresis, and FMTI are no different. But these phenomena should, in theory, have a profound influence on JRS and QAHE. We plan to measure the atomic-scale electronic structure throughout the hysteresis loops of Cr(Bi,Sb)Te3 and V(Bi,Sb)Te3 and thus to visualize the evolution of FM domains and the network of JR states that should exist between regions of opposite magnetization. |
Collaborators |