SKM 2021 – wissenschaftliches Programm
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SYSD: Symposium SKM Dissertation Prize 2021
SYSD 1: Presentations of the Finalists for the 2021 SKM Dissertation Prize
SYSD 1.1: Hauptvortrag
Montag, 27. September 2021, 10:00–10:25, Audimax 2
Avoided quasiparticle decay from strong quantum interactions — •Ruben Verresen1,2,3, Roderich Moessner2, and Frank Pollmann3 — 1Harvard University, Cambridge, USA — 2Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany — 3Technische Universität München, Munich, Germany
The emergent phenomenon of quasiparticles is key to understanding the properties of quantum states of matter. Known to be long lived at the lowest energies, quasiparticles are expected to become unstable when encountering the inevitable continuum of many-particle excited states at high energies, where decay is kinematically allowed. In this talk, I will show that although this expectation is correct for weak interactions, quasiparticles are generically stabilized by strong interactions pushing them out of the continuum. This general mechanism of avoided decay is straightforwardly illustrated in an exactly solvable model. Moreover, we develop a state-of-the-art numerical tool based on tensor networks which allows us to observe avoided decay in the spin-1/2 triangular-lattice Heisenberg antiferromagnet (TLHAF). This is surprising given the expectation of magnon decay in this paradigmatic frustrated magnet. Turning to existing experimental data, we identify the detailed phenomenology of avoided decay in the TLHAF material Ba3CoSb2O9 and even in liquid helium. This mechanism provides a new window into quantum matter in the strongly interacting regime. Moreover, our numerical algorithm gives access to spectral functions for general 2D quantum magnets, providing a direct link between theory and experimental inelastic neutron scattering data.