12,014 research outputs found
Contour surveying system Patent
Describing device for surveying contour of surface using X-Y plotter and traveling transduce
Local density of states in the vortex lattice in a type II superconductor
Local density of states (LDOS) in the triangular vortex lattice is
investigated based on the quasi-classical Eilenberger theory. We consider the
case of an isotropic s-wave superconductor with the material parameter
appropriate to NbSe_2. At a weak magnetic field, the spatial variation of the
LDOS shows cylindrical structure around a vortex core. On the other hand, at a
high field where the core regions substantially overlap each other, the LDOS is
sixfold star-shaped structure due to the vortex lattice effect. The orientation
of the star coincides with the experimental data of the scanning tunneling
microscopy. That is, the ray of the star extends toward the nearest-neighbor
(next nearest-neighbor) vortex direction at higher (lower) energy.Comment: 10 pages, RevTex, 32 figure
Ballistic heat transport of quantum spin excitations as seen in SrCuO2
Fundamental conservation laws predict ballistic, i.e., dissipationless
transport behaviour in one-dimensional quantum magnets. Experimental evidence,
however, for such anomalous transport has been lacking ever since. Here we
provide experimental evidence for ballistic heat transport in a S=1/2
Heisenberg chain. In particular, we investigate high purity samples of the
chain cuprate SrCuO2 and observe a huge magnetic heat conductivity
. An extremely large spinon mean free path of more than a
micrometer demonstrates that is only limited by extrinsic
scattering processes which is a clear signature of ballistic transport in the
underlying spin model
Ground-State Properties of a Rotating Bose-Einstein Condensate with Attractive Interaction
The ground state of a rotating Bose-Einstein condensate with attractive
interaction in a quasi-one-dimensional torus is studied in terms of the ratio
of the mean-field interaction energy per particle to the
single-particle energy-level spacing. The plateaus of quantized circulation are
found to appear if and only if with the lengths of the plateaus
reduced due to hybridization of the condensate over different angular-momentum
states.Comment: 4 pages, 2 figures, Accepted for publication in Physical Reveiw
Letter
Realistic interpretation of a superposition state does not imply a mixture
Contrary to previous claims, it is shown that, for an ensemble of either
single-particle systems or multi-particle systems, the realistic interpretation
of a superposition state that mathematically describes the ensemble does not
imply that the ensemble is a mixture. Therefore it cannot be argued that the
realistic interpretation is wrong on the basis that some predictions derived
from the mixture are different from the corresponding predictions derived from
the superposition state
Theory of I-V Characteristics of Magnetic Josephson Junctions
We analyze the electrical characteristics of a circuit consisting of a free
thin-film magnetic layer and source and drain electrodes that have opposite
magnetization orientations along the free magnet's two hard directions. We find
that when the circuit's current exceeds a critical value there is a sudden
resistance increase which can be large in relative terms if the currents to
source or drain are strongly spin polarized and the free magnet is thin. This
behavior can be partly understood in terms of a close analogy between the
magnetic circuit and a Josephson junction
Crystal and magnetic structure of the oxypnictide superconductor LaO(1-x)FxFeAs: evidence for magnetoelastic coupling
High-resolution and high-flux neutron as well as X-ray powder-diffraction
experiments were performed on the oxypnictide series LaO(1-x)FxFeAs with
0<x<0.15 in order to study the crystal and magnetic structure. The magnetic
symmetry of the undoped compound corresponds to those reported for ReOFeAs
(with Re a rare earth) and for AFe2As2 (A=Ba, Sr) materials. We find an ordered
magnetic moment of 0.63(1)muB at 2 K in LaOFeAs, which is significantly larger
than the values previously reported for this compound. A sizable ordered
magnetic moment is observed up to a F-doping of 4.5% whereas there is no
magnetic order for a sample with a F concentration of x=0.06. In the undoped
sample, several interatomic distances and FeAs4 tetrahedra angles exhibit
pronounced anomalies connected with the broad structural transition and with
the onset of magnetism supporting the idea of strong magneto-elastic coupling
in this material.Comment: 8 pages, 7 figures, regular articl
"Exhaustion" Physics in the Periodic Anderson Model using Iterated Perturbation Theory
We discuss the "exhaustion" problem in the context of the Periodic Anderson
Model using Iterated Perturbation Theory(IPT) within the Dynamical Mean Field
Theory. We find that, despite its limitations, IPT captures the exhaustion
physics, which manifests itself as a dramatic, strongly energy dependent
suppression of the effective Anderson impurity problem. As a consequence, low
energy scales in the lattice case are strongly suppressed compared to the
"Kondo scale" in the single-impurity picture. The IPT results are in
qualitative agreement with recent Quantum Monte Carlo results for the same
problem.Comment: 13 preprint pages including 1 table and 4 eps figures, replaced by
revised version, accepted for publication in Europhysics Letters, added
references and conten
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