Topological spin textures, Berry curvatures, and Hall effects in chiral magnets

Skyrmions are topological solitons that were first discussed in quantum field theory in the 1960’s. In recent years, through a series of beautiful experimental developments, they have become of great relevance to condensed matter physics, especially in chiral magnets. In addition to their fundamental interest as topological spin textures, magnetic skyrmions are also likely to have interesting applications.

I will begin with a pedagogical introduction to what skyrmions are and how they are stabilized in magnetic materials with broken inversion symmetry and spin-orbit coupling. In the second half of my talk, I will describe recent theoretical progress [1,2] on understanding transverse electrical,  thermal, and thermoelectric transport in skyrmion materials. This requires us to understand the effects of phase-space Berry curvature on electron dynamics, with momentum-space Berry curvature of the electronic bands leading to the “anomalous” Hall response and real-space Berry curvature of spin textures leading to the “topological” Hall effect.

 
[1] N. Verma, Z. Addison, M. Randeria, Science Advances 8, eabq2765 (2022)

[2] Z. Addison, L. Keyes, M. Randeria, Phys. Rev. B 108, 014419 (2023) and in preparation.

 
Bio:
Mohit Randeria is a Professor of Physics at The Ohio State University and currently an Infosys Visiting Chair Professor at IISc Bengaluru. His research focuses on correlated and topological quantum materials and condensed matter theory. He obtained a BTech in electrical engineering from IIT Delhi, MS from Caltech, and PhD in theoretical physics from Cornell. After post-doctoral research at the University of Illinois at Urbana-Champaign, he taught at Stony Brook, was on the staff of Argonne National Labs, and on the faculty of the Tata Institute of Fundamental Research, before moving to Ohio State in 2004. He has held visiting professorships at Urbana-Champaign, Berkeley, MIT, and Harvard. He is a winner of the Bhatnagar Award, the ICTP Prize, the IIT Delhi Distinguished Alumni Award, and a Fellow of the American Physical Society and the American Association for the Advancement of Science. He was awarded the 2022 John Bardeen Prize for his work on superconductivity. For more information on his research see: https://u.osu.edu/randeriagroup/