Dresden 2009 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 33: Postersession Correlated Electrons: Metal Insulator Transition, Spin Systems and Itinerant Magnets
TT 33.16: Poster
Mittwoch, 25. März 2009, 14:00–18:00, P1A
Spin-Dynamics of the antiferromagnetic S=1/2-Chain at finite magnetic Fields and intermediate Temperatures — •Simon Grossjohann and Wolfram Brenig — Institut für theoretische Physik, Technische Universität Braunschweig
We present results for the dynamic structure factor of the antiferromagnetic spin-1/2 Heisenberg chain at finite temperatures and finite magnetic fields. Using Quantum-Monte-Carlo based on the stochastic series expansion and Maximum-Entropy methods we detail the evaluation of longitudinal and transverse dynamic structure factors Sαβ(q, ω) with αβ∈ zz, xx, +−, −+ from vanishing magnetic fields up to and above the threshold Bc for ferromagnetic saturation, as well as for high and for intermediate temperatures. The field-induced redistribution of spectral weight was focus of our studies, contrasting longitudinal versus transverse excitations. At finite fields below saturation incommensurate low-energy modes are found to be consistent with zero temperature Bethe-Ansatz. The crossover between the field induced ferromagnet above Bc and the Luttinger liquid below Bc is analyzed in terms of the transverse spin-dynamics and compared to T1-relaxation rates on CuPzN. Finally we assess the quality of the analytic continuations by evaluating sum-rules and detailed balance to demonstrate excellent consistency of the Maximum-Entropy results.