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MA: Fachverband Magnetismus
MA 1: Computational Magnetism I
MA 1.10: Vortrag
Montag, 16. März 2020, 12:00–12:15, HSZ 04
Variational Monte Carlo approach for the dynamical spectra of frustrated spin systems — •Francesco Ferrari1,2 and Federico Becca3 — 1Institut für Theoretische Physik, Goethe-Universität Frankfurt, Frankfurt Am Main (Germany) — 2SISSA-ISAS, International School for Advanced Studies, Trieste (Italy) — 3Università degli Studi di Trieste, Trieste (Italy)
Inelastic neutron-scattering experiments provide fundamental insights into the behavior of magnetic systems and constitute the method of choice for the detection of the spin-liquid phase in candidate materials. However, the theoretical and numerical calculation of dynamical spectra, which are directly measured in neutron-scattering experiments, represents a formidable task in the context of frustrated magnetism. In our work, we employ an efficient variational Monte Carlo scheme to compute the spin dynamical structure factor of frustrated spin models.
We present our numerical results for the dynamical spectra of the antiferromagnetic J1-J2 Heisenberg model on the triangular lattice [1]. In the Heisenberg limit (J2=0), where the system is magnetically ordered, our variational spectra display a well-defined magnon branch, in contrast with spin-wave predictions of spontaneous magnon decay, and in agreement with recent DMRG calculations and inelastic neutron-scattering experiments on Ba3CoSb2O9. When frustration is included, the system undergoes a phase transition to a spin-liquid phase, whose spectral features indicate the presence of fractionalized spinon excitations, and highlight the important role played by gauge fluctuations.
[1] F. Ferrari and F. Becca, Phys. Rev. X 9, 031026 (2019).