SKM 2023 – wissenschaftliches Programm
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 11: Crystal Structure Defects / Real Structure / Microstructure
KFM 11.8: Vortrag
Donnerstag, 30. März 2023, 16:35–16:55, POT 51
Pfaffian invariant identifies magnetic obstructed atomic insulators — •Daniel Varjas1,2,3,4, Isidora Araya Day3,4, Anastasiia Varentcova3, and Anton R. Akhmerov3 — 1Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany — 2Department of Physics, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden — 3QuTech, Delft University of Technology, Delft 2600 GA, The Netherlands — 4Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 4056, 2600 GA Delft, The Netherlands
We derive a Z4 topological invariant that extends beyond symmetry eigenvalues and Wilson loops and classifies two-dimensional insulators with a C4 T symmetry. To formulate this invariant, we consider an irreducible Brillouin zone and constrain the spectrum of the open Wilson lines that compose its boundary. We fix the gauge ambiguity of the Wilson lines by using the Pfaffian at high symmetry momenta. As a result, we distinguish the four C4 T-protected atomic insulators, each of which is adiabatically connected to a different atomic limit. We establish the correspondence between the invariant and the obstructed phases by constructing both the atomic limit Hamiltonians and a C4 T-symmetric model that interpolates between them. The phase diagram shows that C4 T insulators allow ± 1 and 2 changes of the invariant, where the latter is overlooked by symmetry indicators.