Regensburg 2022 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 25: Topological Semimetals
TT 25.12: Talk
Thursday, September 8, 2022, 12:45–13:00, H3
Multifold Hopf semimetals — •Ansgar Graf and Frédéric Piéchon — Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405, Orsay, France
Three-dimensional (3D) topological semimetals exhibit linear energy band crossings that act as monopole sources of Berry curvature. Here, we introduce multifold Hopf semimetals (MHSs), which feature linear N-fold crossing points each of which acts as a Berry dipole. We construct models with N=3,4,5 bands and show that their physical properties are crucially affected by the Berry dipole: First, it makes the Landau level spectrum strongly dependent on the orientation of an external magnetic field. Second, it causes an anomalous Hall effect and weak field magnetoconductivities resembling the chiral anomaly, chiral magnetic and magnetochiral effects familiar from a pair of coupled Weyl nodes. Gapping out MHSs, we obtain multiband Hopf insulators (MHIs) with Hopf numbers up to NHopf=10. MHSs and MHIs provide a fertile playground to explore delicate topology and exhibit analogies to 2D Dirac semimetals and Chern insulators.