415 research outputs found
Spin motive forces due to magnetic vortices and domain walls
We study spin motive forces, i.e, spin-dependent forces, and voltages induced
by time-dependent magnetization textures, for moving magnetic vortices and
domain walls. First, we consider the voltage generated by a one-dimensional
field-driven domain wall. Next, we perform detailed calculations on
field-driven vortex domain walls. We find that the results for the voltage as a
function of magnetic field differ between the one-dimensional and vortex domain
wall. For the experimentally relevant case of a vortex domain wall, the
dependence of voltage on field around Walker breakdown depends qualitatively on
the ratio of the so-called -parameter to the Gilbert damping constant,
and thus provides a way to determine this ratio experimentally. We also
consider vortices on a magnetic disk in the presence of an AC magnetic field.
In this case, the phase difference between field and voltage on the edge is
determined by the parameter, providing another experimental method to
determine this quantity.Comment: 8 pages, 9 figures, submitted to PR
Hidden order in bosonic gases confined in one dimensional optical lattices
We analyze the effective Hamiltonian arising from a suitable power series
expansion of the overlap integrals of Wannier functions for confined bosonic
atoms in a 1d optical lattice. For certain constraints between the coupling
constants, we construct an explicit relation between such an effective bosonic
Hamiltonian and the integrable spin- anisotropic Heisenberg model. Therefore
the former results to be integrable by construction. The field theory is
governed by an anisotropic non linear -model with singlet and triplet
massive excitations; such a result holds also in the generic non-integrable
cases. The criticality of the bosonic system is investigated. The schematic
phase diagram is drawn. Our study is shedding light on the hidden symmetry of
the Haldane type for one dimensional bosons.Comment: 5 pages; 1 eps figure. Revised version, to be published in New. J.
Phy
Field induced d_x^2-y^2+id_xy state in d-density-wave metals
We argue that the d_{xy} component of the order parameter can be generated to
form the d_x^2-y^2+id_xy-density wave state by the external magnetic field. The
driving force for this transition is the coupling of the magnetic field with
the orbital magnetism. The fully gapped particle spectrum and the magnetically
active collective mode of the condensate are discussed as a possible signature
of the d+id' density wave state.Comment: 5 pages, 2 color figure
Geometry and the Hidden Order of Luttinger Liquids: the Universality of Squeezed Space
We present the case that Luttinger liquids are characterized by a form of
hidden order which is similar, but distinct in some crucial regards, to the
hidden order characterizing spin-1 Heisenberg chains. We construct a string
correlator for the Luttinger liquid which is similar to the string correlator
constructed by den Nijs and Rommelse for the spin chain. From a geometric
prespective on the so-called `squeezed space' construction, we demonstrate that
the physics at long wavelength can be reformulated in terms of a gauge
theory. Peculiarly, the normal spin chain lives at infinite gauge coupling
where it is characterized by deconfinement. We identify the microscopic
conditions required for confinement thereby identifying a novel phase of the
spin-chain. We demonstrate that the Luttinger liquid can be approached in the
same general framework. The difference from the spin chain is that the gauge
sector is critical in the sense that the Luttinger liquid is at the phase
boundary where the local symmetry emerges. We evaluate the string
correlator analytically and show that the squeezed space structure is present
both for the strongly coupled Hubbard model and the non-interacting fermion
gas. These structures are hard-wired in the mathematical structure of
bosonization and this becomes obvious by considering string correlators.
Numerical results are presented for the string correlator using a non-abelian
version of the density matrix renormalization group algorithm, confirming in
detail the expectations following from the theory. We conclude with some
observations regarding the generalization of bosonization to higher dimensions.Comment: 24 pages, 14 eps figures, Revtex
Aerosol Route to Antibacterial Nanosilver Coating of Cotton Fabrics
The paper describes a gas phase process for the preparation of cotton fabrics coated with silver nanoparticles as antimicrobial agents. Silver nanoparticles are synthesized by means of atmospheric pressure electrical discharges (spark discharge and glow discharge) in pure inert gases, and the aerosols are passed through cotton fabric samples, where nanoparticles deposit. The particle size distribution of the aerosols is measured online during synthesis. Also, the cristallinity, size and morphology of the silver particles are analyzed. The mean size of the primary particles of silver varies from 4 nm to 18 nm, depending upon the type of discharge, the nature and flow rate of the gas. The bactericidal activity of the cotton samples doped with silver nanoparticles is assessed following the ISO 20743 method. All cotton samples show significant bactericidal property, although it degrades with increasing primary particle size and particle agglomeration. This purely physical aerosol route is a promising sustainable method for nanocoating of textiles
Quasiparticle States around a Nonmagnetic Impurity in D-Density-Wave State of High- Cuprates
Recently Chakravarty {\em et al.} proposed an ordered -density wave (DDW)
state as an explanation of the pseudogap phase in underdoped high-temperature
cuprates. We study the competition between the DDW and superconducting ordering
based on an effective mean-field Hamiltonian. We are mainly concerned with the
effect of the DDW ordering on the electronic state around a single nonmagnetic
impurity. We find that a single subgap resonance peak appears in the local
density of state around the impurity. In the unitary limit, the position of
this resonance peak is always located at with respect to the Fermi
energy. This result is dramatically different from the case of the pure
superconducting state for which the impurity resonant energy is approximately
pinned at the Fermi level. This can be used to probe the existence of the DDW
ordering in cuprates.Comment: 4 pages, 4 figure
Once daily versus three times daily mesalazine granules in active ulcerative colitis: a double-blind, double-dummy, randomised, non-inferiority trial
A list of investigators of the International Salofalk OD Study Group is given in the appendix. Investigators from Latvia are: Jelena Derova, Aleksejs Derovs, Juris Pokrotnieks, Aldis Pukitis, Mairita Ergle.Objectives: To determine the therapeutic equivalence and safety of once daily (OD) versus three times daily (TID) dosing of a total daily dose of 3 g Salofalk (mesalazine) granules in patients with active ulcerative colitis. Design: A randomised, double-blind, double-dummy, parallel group, multicentre, international, phase III noninferiority study. Setting: 54 centres in 13 countries. Patients: 380 patients with confirmed diagnosis of established or first attack of ulcerative colitis (clinical activity index (CAI)>4 and endoscopic index ≥ 4 at baseline) were randomised and treated. Interventions: 8-week treatment with either 3 g OD or 1 g TID mesalazine granules. Main outcome measures: Clinical remission (CAI ≤ 4) at study end. Results: 380 patients were evaluable for efficacy and safety by intention-to-treat (ITT); 345 for per protocol (PP) analysis. In the ITT population, 79.1% in the OD group (n = 191) and 75.7% in the TID group (n = 189) achieved clinical remission (p<0.0001 for non-inferiority). Significantly more patients with proctosigmoiditis achieved clinical remission in the OD group (86%; n = 97) versus the TID group (73%; n = 100; p = 0.0298). About 70% of patients in both treatment groups achieved endoscopic remission, and 35% in the OD group and 41% in the TID group achieved histological remission. About 80% of all patients preferred OD dosing. Similar numbers of adverse events occurred in 55 patients (28.8%) in the OD group and in 61 patients (32.3%) in the TID group, indicating that the two dosing regimens were equally safe and well tolerated. Conclusions: OD 3 g mesalazine granules are as effective and safe as a TID 1 g schedule. With respect to the best possible adherence of patients to the treatment, OD dosing of mesalazine should be the preferred application mode in active ulcerative colitis. ClinicalTrials.gov Identifier: NCT00449722.publishersversionPeer reviewe
Mechanism of pseudogap probed by a local impurity
The response to a local strong non-magnetic impurity in the pseudogap phase
is examined in two distinctly different scenarios: phase-fluctuation (PF) of
pairing field and d-density-wave (DDW) order. In the PF scenario, the resonance
state is generally double-peaked near the Fermi level, and is abruptly
broadened by vortex fluctuations slightly above the transition temperature. In
the DDW scenario, the resonance is single-peaked and remains sharp up to
gradual intrinsic thermal broadening, and the resonance energy is analytically
determined to be at minus of the chemical potential.Comment: 4 pages, 2 figure
Exact results on the Kitaev model on a hexagonal lattice: spin states, string and brane correlators, and anyonic excitations
In this work, we illustrate how a Jordan-Wigner transformation combined with
symmetry considerations enables a direct solution of Kitaev's model on the
honeycomb lattice. We (i) express the p-wave type fermionic ground states of
this system in terms of the original spins, (ii) adduce that symmetry alone
dictates the existence of string and planar brane type correlators and their
composites, (iii) compute the value of such non-local correlators by employing
the Jordan-Wigner transformation, (iv) affirm that the spectrum is
inconsequential to the existence of topological quantum order and that such
information is encoded in the states themselves, and (v) express the anyonic
character of the excitations in this system and the local symmetries that it
harbors in terms of fermions.Comment: 14 pages, 7 figure
Direct observation of incommensurate magnetism in Hubbard chains
The interplay between magnetism and doping is at the origin of exotic
strongly correlated electronic phases and can lead to novel forms of magnetic
ordering. One example is the emergence of incommensurate spin-density waves
with a wave vector that does not match the reciprocal lattice. In one dimension
this effect is a hallmark of Luttinger liquid theory, which also describes the
low energy physics of the Hubbard model. Here we use a quantum simulator based
on ultracold fermions in an optical lattice to directly observe such
incommensurate spin correlations in doped and spin-imbalanced Hubbard chains
using fully spin and density resolved quantum gas microscopy. Doping is found
to induce a linear change of the spin-density wave vector in excellent
agreement with Luttinger theory predictions. For non-zero polarization we
observe a decrease of the wave vector with magnetization as expected from the
Heisenberg model in a magnetic field. We trace the microscopic origin of these
incommensurate correlations to holes, doublons and excess spins which act as
delocalized domain walls for the antiferromagnetic order. Finally, when
inducing interchain coupling we observe fundamentally different spin
correlations around doublons indicating the formation of a magnetic polaron
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