January 28, 2021
1:00-2:00 p.m.
Dr. Igor Altfeder
Ohio State University
ABSTRACT: Spintronics exploits the spin degree of freedom and replaces electron waves with spin waves in signal processing devices for eliminating the energy losses. The new proposed solution for high-performance spintronic materials is based on magnetic topological insulator MnBi2Te4 and axionic metamaterials from MnBi2Te4 family. Axion insulator is a theoretically predicted state of matter capable to mutually convert electric and magnetic signals, and whose properties are reminiscent of cosmological axion dark matter (which explains its name). MnBi2Te4 is the most promising material for realization of solid-state axion insulator. Besides new fundamental physics, axion insulators offer a wide spectrum of applications related to non-linear optics, spintronics, and noise-tolerant quantum computers. This presentation will describe the first experimental realization of room-temperature axionic single-spin switch in topological metamaterial MnBi2Te3/MnBi2Te4. The metamaterial was in situ created in the scanning tunneling microscopy (STM) experiment by removing top Te atomic layer using STM tip. Room temperature STM study of MnBi2Te3/MnBi2Te4 revealed atomic scale variations of exchange gap and formation of nanoscale spin bubbles pinned at subsurface defects. We found that individual spin states in MnBi2Te3 can be reversibly switched using local electric field of STM tip with magnetoelectric response comparable to the theoretically predicted response of axion insulator. The observed topological surface magnetism develops significantly above bulk Néel temperature.
BIOGRAPHY: Igor Altfeder received PhD in Physics from P. Kapitza Institute for Physical Problems of Russian Academy of Sciences in 1993. He held research positions at Harvard University and at Wright Patterson AFB. For his contributions to scanning tunneling microscopy (STM) research Igor Altfeder became a Fellow of the American Physical Society in 2012. The areas of his research at different time included high-Tc superconductors, nanomaterials, two-dimensional materials, and most recently quantum and spintronic materials.