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TT: Fachverband Tiefe Temperaturen

TT 25: Poster Session: Topology

TT 25.16: Poster

Donnerstag, 30. September 2021, 13:30–16:00, P

Non-Hermitian band topology from momentum-dependent relaxation in two dimensional metals with spiral magnetism — •Johannes Mitscherling and Walter Metzner — Max Planck Institute for Solid State Research, Stuttgart, Germany

We present the emergence of non-Hermitian band topology in a two dimensional metal with planar spiral magnetism due to a momentum-dependent relaxation rate. A sufficiently strong momentum dependence of the relaxation rate leads to exceptional points in the Brillouin zone, where the Hamiltonian is non-diagonalizable. The exceptional points appear in pairs with opposite topological charges and are connected by arc-shaped branch cuts. We show that exceptional points inside hole and electron pockets, which are generally present in a spiral magnetic state with a small magnetic gap, can cause a drastic change of the Fermi surface topology by merging those pockets at isolated points in the Brillouin zone. The spectral function observed in photoemission exhibits Fermi arcs. Its momentum dependence is smooth - despite of the non-analyticities in the complex quasiparticle band structure.