**Olle Heinonen**

Argonne National Laboratory

*Spin-charge currents as probes and tools*

Electron currents carry charge, but because electrons also carry spin, electron currents can also transport net spin angular momentum and magnetic moments. This makes electron transport and very useful and versatile probe of electronic structures and magnetic properties, and also a practical tool in devices such as magnetic random access memories. In this seminar, I will give a few very recent examples of spin-charge current effects. The topological Hall effect is a contribution to the Hall effect that arises from Berry curvature, and can be used to probe magnetic skyrmion lattices in magnetic thin films. Topological insulators have very interesting spin-charge currents that arise from the topological surface states. These are electronic surface states that can – in principle – conduct currents without dissipation, and also encode very specific relations between electron momentum and spin direction. Therefore, such surface state currents can be used to efficiently switch the magnetization in an adjacent magnetic insulator. Finally, Weyl semimetals are a class of semimetals for which electronic states also are endowed with non-trivial topological properties. Weyl semimetals also produce strange surface states that give rise to unusual spin-current to charge-current conversions when a spin current is incident from a normal metal onto a magnetic Weyl semimetal.