Seminars

Topological (non-)linear transport and optics.

In this talk, I will give an overview of the theory of anomalous transport and optics in the linear, and particularly in the non-linear regime. I focus on the non-linear Hall, gyrotropic Hall, and circular photogalvanic effects in systems with prominent Berry curvature. I will explicitly discuss the role of impurities, including skew scattering and side jump effects, as well as newly discovered diffractive effects, and will sketch a rigorous derivation of this theory from Keldysh quantum field theory. Both in the linear anomalous Hall effect and in its non-linear or optical counterparts, impurity contributions can be of equal order as intrinsic effects or may even dominate the response. I will also demonstrate that in the diffusive limit, Fick's theory is supplemented by an additional current. Materials applications of the presented theory range from Weyl semimetals and van-der-Waals heterostructures to unconventional superconductors.

The speaker will be happy to stay for discussions after the seminar.

[1] L Powalla, J Kiemle, EJ König, et al.; arXiv:2106.15509,
[2] EJ König, A Levchenko, Annals of Physics; 168492 (2021),
[3] EJ König, M Dzero, A Levchenko, DA Pesin; PRB 99, 155404 (2019),
[4] EJ König, HY Xie, DA Pesin, A Levchenko, PRB 96, 075123 (2017),
[5] EJ König, A Levchenko, PRL, 118 (2), 027001 (2017).