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TT: Fachverband Tiefe Temperaturen

TT 49: CE: Spin Systems and Itinerant Magnets 2

TT 49.8: Vortrag

Donnerstag, 17. März 2011, 16:00–16:15, HSZ 03

Coherent spin-current oscillations in transverse magnetic fields — •Robin Steinigeweg¹, Stephan Langer², Fabian Heidrich-Meisner², Ian P. McCulloch³, and Wolfram Brenig¹ — ¹Institute for Theoretical Physics, Technical University Braunschweig, D-38106 Braunschweig, Germany — ²Department of Physics, Ludwig-Maximilians-Universitaet Muenchen, D-80333 Muenchen, Germany — ³School of Physical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia

This work addresses coherence properties in the dynamics of spin-currents with components transverse to an externally applied magnetic field for the spin-1/2 Heisenberg chain. We study two cases, first, the linear-response regime at finite temperatures, and second, the real-time dynamics of spin currents during the evolution from initial states with an inhomogeneous transverse magnetization. Apart from a coherent oscillation at the Larmor frequency linked to the integrability of the model we find a second nontrivial collective oscillation at higher frequencies, emerging at low temperatures. We clarify that this oscillation is a many-magnon effect and also becomes coherent at lower temperatures. The collective oscillation frequency and life-time is investigated as a function of temperature and magnetic field, with a satisfying agreement between the two approaches employed.