Research Highlights
Optical manifestations and bounds of topological Euler class
Discovery of general bounds on multi-gap optical processes
Quadratic Euler node with nontrivial patch Euler class. The associated eigenstate frame winding (colored vectors) corresponds to the winding of the non-Abelian connection, which is singular at the node. An optical transition within the Euler band subspace is schematically shown
We demonstrate in a recent Editors'suggestion that multigap topological phases relate to new quantum-geometric bounds. These bounds constrain optical weights and sizes of adjacent gaps. The results are validated upon recasting them as optical absorption rates and open up a route to experimentally determine the topological Euler class through momentum and frequency-resolved measurements. We additionally show that a singular quantum geometry of topological Euler band nodes induces observable features such as quantized optical conductivities.
Optical manifestations and bounds of topological Euler class, Wojciech J. Jankowski, Arthur S. Morris, Adrien Bouhon, F. Nur Ünal and Robert-Jan Slager, Phys. Rev. B 111, L081103 (2025), Editors'suggestion.