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TT: Fachverband Tiefe Temperaturen

TT 51: Topological Semimetals II

TT 51.7: Talk

Wednesday, March 20, 2024, 16:30–16:45, H 3007

Fundamental laws of chiral band crossings — •Kirill Alpin1, Moritz M. Hirschmann1,2, Niclas Heinsdorf1,3, Andreas Leonhardt1, Wan Yee Yau1,4, Xianxin Wu1,5, and Andreas P. Schnyder11Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany — 2RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan — 3Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver BC V6T 1Z4, Canada — 4Institute for Theoretical Physics III, University of Stuttgart, D-70550 Stuttgart, Germany — 5Institute for Theoretical Physics, Chinese Academy of Sciences, Beijing, China

We derive two fundamental laws of chiral band crossings: (i) a local constraint relating the Chern number to phase jumps of rotation eigenvalues and (ii) a global constraint determining the number of chiral crossings on rotation axes. Together with the fermion doubling theorem, these laws describe all conditions that a network of chiral band crossing must satisfy. We apply the fundamental laws to prove the existence of enforced double Weyl points, nodal planes, and generic Weyl points, among others. Combining the local constraint with explicit low-energy models, we determine the generic topological phase diagrams of all multifold crossings. Remarkably, we find a fourfold crossing with Chern number 5, which exceeds the previously conceived maximum Chern number of 4. We identify materials crystallizing in space group 198, such as B20 materials and BaAsPt, as suitable compounds with this Chern number 5 crossing.

Keywords: Nodal planes; Weyl points; Multifold crossings; Symmetry; Chern number

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