title: Far-from-equilibrium spin transport in Heisenberg quantum magnets.
abstract: We study experimentally the far-from-equilibrium dynamics in ferromagnetic Heisenberg quantum magnets realized with ultracold atoms in an optical lattice. After controlled imprinting of a spin spiral pattern with an adjustable wave vector, we measure the decay of the initial spin correlations through single-site resolved detection. On the experimentally accessible time scale of several exchange times, we find a profound dependence of the decay rate on the wave vector. In one-dimensional systems, we observe diffusionlike spin transport with a dimensionless diffusion coefficient of 0.22(1). We show how this behavior emerges from the microscopic properties of the closed quantum system. In contrast to the one-dimensional case, our transport measurements for two-dimensional Heisenberg systems indicate anomalous superdiffusion.
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hild
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Fukuhara
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Schauß
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Zeiher
authors.affiliation: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA and ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Knap
authors.affiliation: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Eugene
authors.initials: E
authors.lastname: Demler
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany and Ludwig-Maximilians-Universität, Fakultät für Physik, 80799 München, Germany.
authors.forename: Immanuel
authors.initials: I
authors.lastname: Bloch
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Gross