Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 56: Correlated Electrons: Quantum-Critical Phenomena – Theory
TT 56.10: Vortrag
Mittwoch, 18. März 2015, 12:00–12:15, A 053
Spin Dynamics of the Heisenberg Bilayer from Quantum Monte Carlo — •Maximilian Lohöfer1, Stefan Wessel1, Frederic Mila2, Tommaso Coletta2, and Fakher Assaad3 — 1Institute for Theoretical Solid State Physics, RWTH Aachen — 2Institut de théorie des phénomènes physiques, Ecole polytechnique fédérale de Lausanne — 3Institut für Theoretische Physik und Astrophysik, Universität Würzburg
The spin-1/2 Heisenberg model on the square lattice blayer provides a basic example to study quantum critical behavior in interacting quantum spin systems. While its static equilibrium properties have been intensively investigated in the past, thus far only few studies have discussed the details of the reconstruction of the excitation spectrum across the quantum phase transition between the antiferromagnetically ordered phase and the quantum disordered regime. Here, based on stochastic series expansion quantum Monte Carlo (SSE) simulations and stochastic analytic continuation (SAC) methods, we calculate the dynamical spin structure factors in this model in different symmetry sectors. We analyse the evolution of the low-energy modes, related to Goldstone modes as well as the longitudinal amplitude mode in the ordered phase upon crossing through the quantum critical point and consider the corresponding restoration of the SU(2) symmetry in the disordered regime. The obtained spectra are also discussed in view of results from series expansions, improved spin wave theory and strong-dimer perturbation theory.