Berlin 2024 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 51: Topological Semimetals II

TT 51.8: Talk

Wednesday, March 20, 2024, 16:45–17:00, H 3007

Topological responses from gapped Weyl points in 2D altermagnets — •Raymond Wiedmann, Kirill Parshukov, and Andreas P. Schnyder — Max Planck Institute for Solid State Research, Stuttgart, Germany

Altermagnetism combines aspects of both ferromagnetism and antiferromagnetism, breaking spin degeneracy while possessing no net magnetization. In this work, we study the symmetry requirements for topologically protected Weyl points involving bands with the same spin quantum number in two-dimensional altermagnets and list all spin-wallpaper groups enabling this feature. For one of them, we construct an electronic tight-binding model and a magnonic linear spin-wave model and investigate the implications of these novel topological band degeneracies, which are protected by a quantized π-Berry phase. Introducing different mass terms we gap out the Weyl points and study the emerging topological insulating phases. We find phases with a finite Chern and spin Chern number, leading to topologically protected edge states and anomalous electronic and thermal Hall responses. We calculate the quantum (spin) Hall and the topological thermal Hall effect for the different topological phases in the electron and magnon models, respectively.

Keywords: quantum geometry; Weyl semimetal; anomalous Hall effect; optical conductivity; symmetry-protected topological phase