# Regensburg 2019 – wissenschaftliches Programm

## Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

# TT: Fachverband Tiefe Temperaturen

## TT 37: Topological Semimetals - Theory (joint session TT/MA)

### TT 37.6: Vortrag

### Mittwoch, 3. April 2019, 10:45–11:00, H22

**Photo-induced anomalous Hall effect in nodal-line semimetals** — •Andreas Leonhardt and Andreas P. Schnyder — Max Planck Institute for Solid State Research

Spatial symmetries like reflection or *PT*-symmetry are able to
protect band crossings along closed lines in the Brillouin zone at
momenta left invariant by the symmetry. These nodal-lines carry a
topological charge, characterized by a quantized Berry phase.
This implies a divergent Berry curvature at these topological
defects.

In semi-classical transport theory, a non-vanishing Berry curvature is associated with an anomalous velocity. In most cases however, the contributions from opposite points in the Brillouin zone cancel exactly, such that no anomalous Hall effect can be observed. Since circular polarized light couples differently to positive and negative momenta, the cancellation of anti-symmetric terms can be lifted, leading to a non-vanishing Hall current that changes direction with switching the polarization.

We describe the lattice model of a nodal-line semimetal driven by circular polarized light in the Floquet formalism. Coupling this system to leads with a potential difference allows us to calculate the Hall current in the Keldysh formalism. We investigate the relation of the photo-induced Hall conductivity to material characteristics and light amplitude and frequency and provide estimates for the required intensities and magnitude of the effect for some known nodal-line compounds.