Regensburg 2019 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 33: Frustrated Magnets - General 2 (joint session TT/MA)
TT 33.1: Talk
Tuesday, April 2, 2019, 14:00–14:15, Theater
Strong quantum interactions prevent quasiparticle decay — •Ruben Verresen1,2, Roderich Moessner1, and Frank Pollmann2 — 1Max-Planck-Institute for the Physics of Complex Systems — 2Technical University of Munich
Quantum states of matter typically exhibit collective excitations known as quasiparticles. Known to be long-lived at the lowest energies, common wisdom says that quasiparticles become unstable when they encounter the inevitable continuum of many-particle excited states at high energies. Whilst correct for weak interactions, we show that this is far from the whole story: strong interactions generically stabilise quasiparticles by pushing them out of the continuum. This general mechanism is straightforwardly illustrated in an exactly solvable model. Using state-of-the-art numerics, we find it at work also in the spin-1/2 triangular lattice Heisenberg antiferromagnet (TLHAF) near the isotropic point---this is surprising given the common 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---one of the earliest instances of quasiparticle decay.