Topological Hall effect in a system with magnetic skyrmions

2018-01-30 13:15:00 2018-01-30 14:15:00 Europe/Helsinki Topological Hall effect in a system with magnetic skyrmions LTL Quantum Physics Seminar (Nanotalo). Speaker: Dr. Igor Rozhansky (Ioffe Institute, Russia). http://physics.aalto.fi/en/midcom-permalink-1e7f12670ffb7f4f12611e796c611977369f3b1f3b1 Puumiehenkuja 2, 02150, Espoo

LTL Quantum Physics Seminar (Nanotalo). Speaker: Dr. Igor Rozhansky (Ioffe Institute, Russia).

30.01.2018 / 13:15 - 14:15
Nanotalo, 161, Puumiehenkuja 2, 02150, Espoo, Otaniemi, FI

Topological Hall effect (THE) is a recently discovered transport phenomenon occurring in various magnetic systems due to free carriers exchange interaction with chiral magnetization textures, such as magnetic skyrmions. THE is considered as a perspective tool to probe topologically nontrivial spin structures as well as for potential device applications such as racetrack memory.

Despite its great importance, THE has still lacked a proper theoretical description. The existing theories considered two limiting cases of either infinitely strong exchange interaction when the geometric Berry phase approach is applicable or the case of a weak exchange interaction allowing for perturbation theory analysis. These two approaches give qualitatively different results. The Berry phase approximation has revealed that THE is accompanied with a transverse spin current so the appearance of charge Hall current requires spin polarization of the carriers. In the opposite case of a weak exchange the transverse charge current occurs in the absence of a spin current and THE is expected even for non-polarized carriers.

We have developed a theory of THE based on exact solution of a problem of electron scattering on a chiral spin field. We show how the transverse charge current in the weak coupling case transforms into a transverse spin current in the adiabatic regime. Another interesting finding is that unlike previously thought the topological charge of a magnetic skyrmion is not crucial for THE. Chiral magnetic vortices exhibit THE similar to that in magnetic skyrmions.