Spin chirality driven by thermal fluctuation processes in magnetic insulators and metals

Max Hirschberger
Department of Applied Physics of the University of Tokyo
Thursday, March 10, 2022
11:00 am
ISEB 1310 [Interdisciplinary Science and Engineering Building]

Chirality is an ubiquitous concept in the natural sciences, distinguishing left / right-handed objects or processes. In magnetic solids, the chirality of spin textures is derived from the twisting habit of neighboring atomic spins. I will discuss dynamical processes, specifically thermal fluctuation processes, which are transient but generate a net chiral habit in a magnetic solid. Through their coupling to local magnetic moments, conduction electrons feel this chiral habit; hence, (thermo-) electric transport coefficients, which are time-averaged quantities, allow us to distinguish two scenarios: (1) Short-range spin correlations, where a small cluster of magnetic moments is sufficient to describe the physical properties of the thermally disordered solid and (2) Longer-range correlations, such as dynamically nucleating and decaying skyrmions. I introduce toy model systems which realize Kagome and triangular lattices of magnetic moments, and discuss the role of lattice geometry in promoting these fluctuation phenomena. Finally, I will show that the thermal Hall effect of magnetic insulators can also have a contribution related to thermal fluctuations with chiral habit.

Judit Romhanyi