108 research outputs found
Spin-charge coupling in quantum wires at zero magnetic field
We discuss an approximation for the dynamic charge response of nonlinear
spin-1/2 Luttinger liquids in the limit of small momentum. Besides accounting
for the broadening of the charge peak due to two-holon excitations, the
nonlinearity of the dispersion gives rise to a two-spinon peak, which at zero
temperature has an asymmetric line shape. At finite temperature the spin peak
is broadened by diffusion. As an application, we discuss the density and
temperature dependence of the Coulomb drag resistivity due to long-wavelength
scattering between quantum wires.Comment: 16 pages, 5 figures. This is an extended version of "Coulomb drag
from spin-charge coupling at zero magnetic field
Disentangling Scaling Properties in Anisotropic Fracture
Structure functions of rough fracture surfaces in isotropic materials exhibit
complicated scaling properties due to the broken isotropy in the fracture plane
generated by a preferred propagation direction. Decomposing the structure
functions into the even order irreducible representations of the SO(2) symmetry
group (indexed by ) results in a lucid and quickly convergent
description. The scaling exponent of the isotropic sector () dominates at
small length scales. One can reconstruct the anisotropic structure functions
using only the isotropic and the first non vanishing anisotropic sector ()
(or at most the next one ()). The scaling exponent of the isotropic sector
should be observed in a proposed, yet unperformed, experiment.Comment: 5 pages, 8 figure
Adiabatic Pumping in Interacting Systems
A dc current can be pumped through an interacting system by periodically
varying two independent parameters such as magnetic field and a gate potential.
We present a formula for the adiabatic pumping current in general interacting
systems, in terms of instantaneous properties of the system, and find the
limits for its applicability. This formula generalizes the scattering approach
for noninteracting pumps. We study the pumped spin in a system that exhibits
the two-channel Kondo effect as an application of the adiabatic pumping
formula. We find that a quantized spin of is transferred between the
two channels as the temperature approaches zero, and discuss the non-Fermi
liquid features of this system at finite temperatures.Comment: 4 pages and 1 figur
Condensation of Photons coupled to a Dicke Field in an Optical Microcavity
Motivated by recent experiments reporting Bose-Einstein condensation (BEC) of
light coupled to incoherent dye molecules in a microcavity, we show that due to
a dimensionality mismatch between the 2D cavity-photons and the 3D arrangement
of molecules, the relevant molecular degrees of freedom are collective Dicke
states rather than individual excitations. For sufficiently high dye
concentration the coupling of the Dicke states with light will dominate over
local decoherence. This system also shows Mott criticality despite the absence
of an underlying lattice in the limit when all dye molecules become excited.Comment: 4 pages + supplementary materia
Two-dimensional Valence Bond Solid (AKLT) states from electrons
Two-dimensional AKLT model on a honeycomb lattice has been shown to be a
universal resource for quantum computation. In this valence bond solid,
however, the spin interactions involve higher powers of the Heisenberg coupling
, making these states seemingly unrealistic on
bipartite lattices, where one expects a simple antiferromagnetic order. We show
that those interactions can be generated by orbital physics in multiorbital
Mott insulators. We focus on electrons on the honeycomb lattice and
propose a physical realization of the spin- AKLT state. We find a phase
transition from the AKLT to the Neel state on increasing Hund's rule coupling,
which is confirmed by density matrix renormalization group (DMRG) simulations.
An experimental signature of the AKLT state consists of protected, free
spins-1/2 on lattice vacancies, which may be detected in the spin
susceptibility
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