Anomalous Hall effect from spin-group symmetry breaking
by
Tsung-Dao Lee Institute/N4F-N400 - meeting room
Tsung-Dao Lee Institute
Host: Prof. Anyuan Gao
Venue: TDLI Meeting Room N400
Tencent Meeting link: https://meeting.tencent.com/dm/eSa1BHPr3jvN
Meeting ID: 881924098, no password
Abstract:
The anomalous Hall effect is one of the most fundamental phenomena in solid state physics. Traditionally, it is viewed as a time-reversal-symmetry-breaking phenomenon and the resulting conductivity is governed by the Onsager’s reciprocal relation, i.e., . In experiments, such relation is generally taken at the linear order of
, yielding an empirical law employed in many previous literatures. However, in strong magnets, the exchange energy associated with the magnetic order is usually comparable with other energy scales, rendering such power series expansion over
to be inappropriate. In this talk, I will show that it is more informative to reformulate the anomalous Hall effect as a spin-group-symmetry-breaking phenomenon by treating the spin-orbit coupling as perturbation, since the latter is usually much smaller than exchange and hopping energy. Associated with the spin-group-symmetry-breaking, the anomalous Hall effect can exhibit various multipolar anisotropy when the spin order is rotated globally. Our theory applies to ferromagnets, collinear and non-collinear antiferromagnets. Out of equilibrium, such multipolar anisotropy contains antisymmetric component, which corresponds to an anomalous Hall current driven by coherent spin wave. Such a signal can be used to probe altermagnets that normally do not show an anomalous Hall effect.
Biography:
Professor Yang Gao got his bachelor’s degree from Peking University in 2009. He then joined Prof. Qian Niu’s group in University of Texas at Austin and got his doctor’s degree in 2016. After that, he joined Prof. Di Xiao’s group in Carnegie Mellon University as a postdoctoral research associate. In 2020, he joined University of Science and Technology of China. Professor Gao’s research focuses on Berry phase effect in nonlinear and nonreciprocal transport and optical phenomena. He has published about 30 papers, with 12 of them in Physical Review Letters, Nature, Nature Communications, and PNAS.
