Dresden 2020 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 65: Poster Session Topological Topics

TT 65.31: Poster

Thursday, March 19, 2020, 15:00–19:00, P2/EG

Interacting magnons in the easy-axis square-lattice XXZ model — •Matthias Walther¹, Götz S. Uhrig², and Kai P. Schmidt¹ — ¹Institut für Theoretische Physik, FAU Erlangen-Nürnberg, 91058 Erlangen, Germany — ²Lehrstuhl für Theoretische Physik I, Technische Universität Dortmund, 44221 Dortmund, Germany

The easy-axis square-lattice XXZ-model interpolates between the Ising model and the isotropic Heisenberg model. The system displays always long-ranged Néel order. However, the elementary excitations, except for the SU(2) symmetric Heisenberg point, correspond to gapped magnons and the spectrum is known to possess multi-magnon bound states. We follow the the excitation spectrum from the Heisenberg to the Ising model in order to find possible connections between , e.g., the amplitude Higgs resonance and the long-lived two-magnon bound states known from the Ising limit. Technically, this is achieved by the method of non-perturbative continuous similarity transformations in momentum space, which has been proven to capture the physics quantitatively in the Heisenberg limit.