Axion topological insulators: interplay of topology and axion electrodynamics | Dr. Maxim Gorlach

Theoretical Seminar at The Department of Physics & Engineering, ITMO | 01 Dec 2021

Timecodes are below the abstract.

Dr. Maxim Gorlach
ITMO University, St. Petersburg, Russia

Title: “Axion topological insulators: interplay of topology and axion electrodynamics”

Abstract: Axions are hypothetical particles that were originally postulated to resolve strong CP problem in quantum chromodynamics and are currently considered as promising dark matter candidates in astrophysics. While the search for cosmic axions is ongoing, some condensed matter systems give rise to the so-called emergent axions. Specifically, electrodynamics of such materials called axion topological insulators is captured by the equations of axion electrodynamics. Recently, axion topological insulators were realized in condensed matter systems. In this educational talk, I will discuss how topology is related to axion electrodynamics in these materials, what is the difference between the first and second Chern number and how nonzero magneto-electric coupling can arise in centrosymmetric materials.
Main paper/arXiv, related to the seminar, and other references
D.M. Nenno, et al. Nature Reviews Physics 2, 682-696 (2020)

0:00:00 Intro
0:00:35 Start of the talk
0:01:35 Equations of axion electrodynamics
0:21:16 3D form of axion electrodynamics equations
0:28:37 Nonreciprocal bianisotropic medium (Tellegen
0:31:45 Axion physics via magneto-electric coupling
0:41:57 Quantum Hall effect and Chern number
0:58:02 Second Chern number and axion term
1:01:23 Solid-state realization of axion topological
1:02:32 Questions

The School of Physics and Engineering of ITMO University (Saint Petersburg, Russia) hosts online weekly seminars to discuss recent scientific achievements of researchers from all over the world with a wide audience. The topics include experimental (Optical seminar) and theoretical (Theoretical seminar) aspects of nanophotonics, solid-state physics, material science, as well as design and applications of radiofrequency structures and devices (Microwave seminar).

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