Regensburg 2013 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 40: Poster Session Correlated Electrons

TT 40.59: Poster

Mittwoch, 13. März 2013, 15:00–19:00, Poster D

Phase Space Berry Phases and Electronic Transport in Magnetic Whirl Structures — •Robert Bamler and Achim Rosch — Universität zu Köln, Cologne, Germany

We present a semi-classical theory of electronic transport in magnetic whirl structures with spin-orbit coupling. Our theory predicts that the magnetic whirls carry an electric charge due to a non-vanishing Berry phase curvature in phase space.

In magnetic materials without inversion symmetry (e.g. MnSi), the spin-orbit coupling can lead to smooth whirls (skyrmions) in the magnetization. The magnetic whirls give rise to an emergent magnetic field that can be measured as a so-called ``topological'' contribution to the Hall signal. The emergent magnetic field is usually explained with the picture that conduction electrons that transverse the system pick up a Berry phase because their spin follows adiabatically the direction of the local magnetization. This explanation neglects the influence of spin-orbit coupling. However, the anomalous Hall effect in MnSi is known to be large, indicating that spin-orbit coupling may be relevant in this material.

In our work, we develop a semi-classical theory of electronic transport in magnetic whirl structures under the influence of spin-orbit coupling. In addition to the emergent magnetic field and the anomalous velocity known from the anomalous Hall effect, new cross-terms arise in the equations of motion and the skyrmions acquire an electric charge due to Berry phases picked up on closed trajectories in mixed coordinate and momentum space.