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TT: Fachverband Tiefe Temperaturen

TT 16: Correlated Electrons: Low-dimensional Systems - Models 2

TT 16.3: Talk

Tuesday, March 27, 2012, 10:00–10:15, H 0104

Spontaneous Quasiparticle Decay in Low-Dimensional Quantum Spin Systems — •Tim Fischer and Götz S. Uhrig — Theoretische Physik I, Technische Universität Dortmund, 44221 Dortmund

In sufficiently dimerized quantum antiferromagnets the elementary excitations are gapped spin S=1 triplon quasiparticles. Although these triplons are protected by a gap at low energies they may decay spontaneously at higher energies where the one-triplon dispersion merges with the two-triplon continuum. The decay implies the breakdown of the quasiparticle picture. No quantitative description by a Lorentzian resonance is possible.

We characterize the decay for low-dimensional quantum antiferromagnets in detail. In particular, three qualitatively different scenarios are identified depending on the one-triplon dispersion and the two-triplon interaction.

Based on the theoretical concepts we analyse the inelastic neutron scattering (INS) results for IPA-CuCl₃ [1]. Starting from the microscopic model obtained by adapted continuous unitary transformations (CUTs) [2] we provide a quantitative description of the decay measured in IPA-CuCl₃ by INS.
T. Masuda et al. (2006) PRL 96 047210
T. Fischer, S. Duffe and G. S. Uhrig (2011) EPL 96 47001