857 research outputs found
The 4-spinon dynamical structure factor of the Heisenberg chain
We compute the exact 4-spinon contribution to the zero-temperature dynamical
structure factor of the spin-1/2 Heisenberg isotropic antiferromagnet in zero
magnetic field, directly in the thermodynamic limit. We make use of the
expressions for matrix elements of local spin operators obtained by Jimbo and
Miwa using the quantum affine symmetry of the model, and of their adaptation to
the isotropic case by Abada, Bougourzi and Si-Lakhal (correcting some overall
factors). The 4-spinon contribution to the first frequency moment sum rule at
fixed momentum is calculated. This shows, as expected, that most of the
remaining correlation weight above the known 2-spinon part is carried by
4-spinon states. Our results therefore provide an extremely accurate
description of the exact structure factor.Comment: 13 page
Spatially Anisotropic Heisenberg Kagome Antiferromagnet
We study the quasi-one-dimensional limit of the spin-1/2 quantum Heisenberg
antiferromagnet on the kagome lattice. The lattice is divided into
antiferromagnetic spin-chains (exchange J) that are weakly coupled via
intermediate "dangling" spins (exchange J'). Using one-dimensional
bosonization, renormalization group methods, and current algebra techniques the
ground state is determined in the limit J'<<J. We find that the dangling spins
and chain spins form a spiral with O(1) and O(J'/J) static moments,
respectively, atop of which the chain spins exhibit a smaller O[(J'/J)^2]
antiferromagnetically ordered component along the axis perpendicular to the
spiral plane.Comment: 17 pages, 3 figures, corrected sign error, corrected typos, updated
reference
Quasiparticles of string solutions in the spin-1/2 antiferromagnetic Heisenberg chain in a magnetic field
Spectral properties of the spin-1/2 antiferromagnetic Heisenberg chain in a
magnetic field are investigated by using exact Bethe-ansatz solutions. We argue
that not only quasiparticles called psinon and antipsinon but also a
quasiparticle representing a 2-string in the Bethe ansatz plays an important
role for dynamical properties in a magnetic field. Combined with psinon and
antipsinon, the quasiparticle for a 2-string forms a continuum in the
high-energy regime for transverse dynamical structure factor
. In the zero-field limit, the continuum is located on the
mode of the lowest excited states in zero field called the des
Cloizeaux-Pearson mode. In a magnetic field, the continuum separates from other
low-energy continua, and reduces to the mode of bound states of overturned
spins from the fully polarized state near the saturation field. We confirm the
relevance through comparisons with available experimental results on the
quasi-one-dimensional antiferromagnet CuCl2N(CD).Comment: 4 pages, 1 figure, 1 tabl
Split Fermi seas in one-dimensional Bose fluids
For the one-dimensional repulsive Bose gas (Lieb-Liniger model), we study a
special class of highly-excited states obtained by giving a finite momentum to
subgroups of particles. These states, which correspond to `splitting' the
ground state Fermi sea-like quantum number configuration, are zero-entropy
states which display interesting properties more normally associated to ground
states. Using a numerically exact method based on integrability, we study these
states' excitation spectrum, density correlations and momentum distribution
functions. These correlations display power-law asymptotics, and are shown to
be accurately described by an effective multicomponent Tomonaga-Luttinger
liquid theory whose parameters are obtained from Bethe Ansatz. The
non-universal correlation prefactors are moreover obtained from integrability,
yielding a completely parameter-free fit of the correlator asymptotics.Comment: 10 pages, 14 figure
Electron Interactions and Transport Between Coupled Quantum Hall Edges
We examine the effects of electron-electron interactions on transport between
edge states in a multilayer integer quantum Hall system. The edge states of
such a system, coupled by interlayer tunneling, form a two-dimensional, chiral
metal at the sample surface. We calculate the temperature-dependent
conductivity and the amplitude of conductance fluctuations in this chiral
metal, treating Coulomb interactions and disorder exactly in the weak-tunneling
limit. We find that the conductivity increases with increasing temperature, as
observed in recent experiments, and we show that the correlation length
characterising conductance fluctuations varies inversely with temperature.Comment: 4 pages, 2 figures, typos corrected, Ref. 17 added, minor changes
made for publicatio
Dynamical density-density correlations in the one-dimensional Bose gas
The zero-temperature dynamical structure factor of the one-dimensional Bose
gas with delta-function interaction (Lieb-Liniger model) is computed using a
hybrid theoretical/numerical method based on the exact Bethe Ansatz solution,
which allows to interpolate continuously between the weakly-coupled
Thomas-Fermi and strongly-coupled Tonks-Girardeau regimes. The results should
be experimentally accessible with Bragg spectroscopy.Comment: 4 pages, 3 figures, published versio
The single-particle density matrix and the momentum distribution of dark "solitons" in a Tonks-Girardeau gas
We study the reduced single-particle density matrix (RSPDM), the momentum
distribution, natural orbitals and their occupancies, of dark "soliton" (DS)
states in a Tonks-Girardeau gas. DS states are specially tailored excited
many-body eigenstates, which have a dark solitonic notch in their
single-particle density. The momentum distribution of DS states has a
characteristic shape with two sharp spikes. We find that the two spikes arise
due to the high degree of correlation observed within the RSPDM between the
mirror points ( and ) with respect to the dark notch at ; the
correlations oscillate rather than decay as the points and are being
separated.Comment: 9 pages, 8 figure
Fractional spinon excitations in the quantum Heisenberg antiferromagnetic chain
Assemblies of interacting quantum particles often surprise us with properties
that are difficult to predict. One of the simplest quantum many-body systems is
the spin 1/2 Heisenberg antiferromagnetic chain, a linear array of interacting
magnetic moments. Its exact ground state is a macroscopic singlet entangling
all spins in the chain. Its elementary excitations, called spinons, are
fractional spin 1/2 quasiparticles; they are created and detected in pairs by
neutron scattering. Theoretical predictions show that two-spinon states exhaust
only 71% of the spectral weight while higher-order spinon states, yet to be
experimentally located, are predicted to participate in the remaining. Here, by
accurate absolute normalization of our inelastic neutron scattering data on a
compound realizing the model, we account for the full spectral weight to within
99(8)%. Our data thus establish and quantify the existence of higher-order
spinon states. The observation that within error bars, the entire weight is
confined within the boundaries of the two-spinon continuum, and that the
lineshape resembles a rescaled two-spinon one, allow us to develop a simple
physical picture for understanding multi-spinon excitations.Comment: 22 pages, 4 figures, Supplementary material
Logarithmic Operators and Dynamical Extention of The Symmetry Group in the Bosonic SU(2)_0 and SUSY SU(2)_2 WZNW Models
We study the operator product expansion in the bosonic and SUSY
WZNW models. We find that these OPEs contain both logarithmic
operators and new conserved currents, leading to an extension of the symmetry
group.Comment: 16 pages, Late
- âŠ