Dresden 2009 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

TT: Fachverband Tiefe Temperaturen

TT 38: Correlated Electrons: Low-dimensional Systems - Models 1

TT 38.2: Vortrag

Donnerstag, 26. März 2009, 09:45–10:00, HSZ 301

A real-time study of diffusive and ballistic transport in spin-1/2 chains using the adaptive time-dependent DMRG method — •Stephan Langer¹, Fabian Heidrich-Meisner¹, Jochen Gemmer², Ian McCulloch³, and Ulrich Schollwoeck¹ — ¹Institut für Theoretische Physik C, RWTH Aachen University, Germany — ²Institut für Theoretische Physik, Universität Osnabrück, Germany — ³The University of Queensland, Brisbane, QLD 4072, Australia

We study spin transport and dynamics in one-dimensional quantum spin-1/2 systems at zero temperature. Using the time-dependent adaptive Density Matrix Renormalization Group (DMRG) method, we follow the time evolution of the magnetization starting from inhomogeneous initial states. Our goal is to distinguish between ballistic and diffusive transport. This is achieved by looking at the long-time behavior of the spatial variance of the magnetization, where, for instance, a quadratic increase in time is indicative of ballistic transport. Applying this to the spin-1/2 XXZ chain, we confirm the established picture of ballistic transport in the critical phase. In the massive phase, strong perturbations are required to drive the dynamics, which show diffusive behavior. Then we turn to two non-integrable models, the two-leg spin-ladder and the frustrated spin chain, for which we find diffusive behavior in all massive phases, but ballistic transport in the gapless phase of the frustrated chain. Since our analysis does not rely on linear-response theory, we can explore the full range of perturbation strength, and, in particular, out-of-equilibrium physics.