Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 19: Correlated Electrons: Quantum-Critical Phenomena
TT 19.12: Vortrag
Dienstag, 26. Februar 2008, 17:15–17:30, H 3010
Quantum Critical Dynamics of the S=1/2 AFM Heisenberg Chain in Finite Magnetic Fields: a QMC Study — •Simon Grossjohann1, Wolfram Brenig1, Hannes Kühne2, and Hans-Henning Klauss2 — 1Institut für Theoretische Physik, TU Braunschweig — 2Institut für Festkörperphysik, TU Dresden
We investigate the field driven quantum critical dynamics of the antiferromagnetic S=1/2 Heisenberg chain using Quantum Monte-Carlo techniques (SSE) and analytic continuation by Maximum Entropy methods. Results for the transverse and longitudinal dynamical structure factor Sαβ(q, ω) will be presented for different temperatures T, with 0.1≤ T/J ≤ 1 and various magnetic fields below and above saturation field hc. In the vicinity of hc, condensation of the elementary excitations of the fully polarized phase induce a diverging longitudinal NMR relaxation rate 1/T1. Such quantum critical slowing down has been observed in recent experiments on Cu(C4H4N2)(NO3)2 and agrees very well with our theoretical findings. In addition our spectra will be shown to be consistent with sum rules for the static structure factor and static susceptibility.