4,587 research outputs found
Thermal transport properties of disordered spin-1/2 systems
This work studies heat transport of bond-disordered spin-1/2 chains. As an
example, the XX case is analyzed, which corresponds to a model of
noninteracting spinless fermions. Within the fermion representation, the
single-particle eigenenergies are determined numerically, which allow one to
compute transport coefficients. Since the ballistic transport properties of a
clean chain are destroyed by disorder, the focus is on the frequency dependence
of the thermal conductivity and on a qualitative comparison with the spin
conductivity, both at finite temperatures.Comment: 2 pages, 1 figure. To be published in the Proceedings of SCES '05,
Vienna, in Physica
Transport in dimerized and frustrated spin systems
We analyze the Drude weight for both spin and thermal transport of
one-dimensional spin-1/2 systems by means of exact diagonalization at finite
temperatures. While the Drude weights are non-zero for finite systems, we find
indications of a vanishing of the Drude weights in the thermodynamic limit for
non-integrable models implying normal transport behavior.Comment: 2 pages, 1 figure. Proceedings of the ICM 2003, Rom
Quantum phases of strongly-interacting bosons on a two-leg Haldane ladder
We study the ground-state physics of a single-component Haldane model on a
hexagonal two-leg ladder geometry with a particular focus on strongly
interacting bosonic particles. We concentrate our analysis on the regime of
less than one particle per unit-cell. As a main result, we observe several
Meissner-like and vortex-fluid phases both for a superfluid as well as a
Mott-insulating background. Furthermore, we show that for strongly interacting
bosonic particles an unconventional vortex-lattice phase emerges, which is
stable even in the regime of hardcore bosons. We discuss the mechanism for its
stabilization for finite interactions by a means of an analytical
approximation. We show how the different phases may be discerned by measuring
the nearest- and next-nearest-neighbor chiral currents as well as their
characteristic momentum distributions.Comment: 13 pages, 20 figure
Transport in quasi one-dimensional spin-1/2 systems
We present numerical results for the spin and thermal conductivity of
one-dimensional (1D) quantum spin systems. We contrast the properties of
integrable models such as the spin-1/2 XXZ chain against nonintegrable ones
such as frustrated and dimerized chains. The thermal conductivity of the XXZ
chain is ballistic at finite temperatures, while in the nonintegrable models,
this quantity is argued to vanish. For the case of frustrated and dimerized
chains, we discuss the frequency dependence of the transport coefficients.
Finally, we give an overview over related theoretical work on intrinsic and
extrinsic scattering mechanisms of quasi-1D spin systems.Comment: 11 pages, 7 figure
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