405 research outputs found
Calculation of NMR Properties of Solitons in Superfluid 3He-A
Superfluid 3He-A has domain-wall-like structures, which are called solitons.
We calculate numerically the structure of a splay soliton. We study the effect
of solitons on the nuclear-magnetic-resonance spectrum by calculating the
frequency shifts and the amplitudes of the soliton peaks for both longitudinal
and transverse oscillations of magnetization. The effect of dissipation caused
by normal-superfluid conversion and spin diffusion is calculated. The
calculations are in good agreement with experiments, except a problem in the
transverse resonance frequency of the splay soliton or in magnetic-field
dependence of reduced resonance frequencies.Comment: 15 pages, 10 figures, updated to the published versio
Zinc Deficiency Symptoms of Beans
Zinc deficiency is common (2) on bean plants grown on calcareous
Portneuf silt loam in the Magic Valley of southern Idaho. Ten pounds of zinc
per acre every third year is recommended for prevention (4). Land leveling
or deep plowing brings to the surface the highly calcareous subsoil and intensifies
the zinc deficiency problem. Beans grown following sugar beets or high
manure or phosphate fertilizer applications are more likely to exhibit zinc
deficiency symptoms (4)
Condensation Energy and High Tc Superconductivity
From an analysis of the specific heat of one of the cuprate superconductors
it is shown, that even if a large part of the experimental specific heat
associated with the superconducting phase transition is due to fluctuations,
this part must be counted when one tries to extract the condensation energy
from the data. Previous work by Chakravarty, Kee and Abrahams, where the
fluctuation part was subtracted, has resulted in an incorrect estimation of the
condensation energy.Comment: 4 pages, 5 encapsulated Postscript figures, uses ReVTeX.st
Condensation energy in strongly coupled superconductors
We consider the condensation energy in superconductors where the pairing is
electronic in origin and is mediated by a collective bosonic mode.
We use magnetically-mediated superconductivity as an example, and show that
for large spin-fermion couplings, the physics is qualitatively different from
the BCS theory as the condensation energy results from the feedback on spin
excitations, while the electronic contribution to the condensation energy is
positive due to an ``undressing'' feedback on the fermions. The same feedback
effect accounts for the gain of the kinetic energy at strong couplings.Comment: 4 pages, revtex 4, 3 eps figure
Periodic Vortex Structures in Superfluid 3He-A
We discuss the general properties of periodic vortex arrangements in rotating
superfluids. The different possible structures are classified according to the
symmetry space-groups and the circulation number. We calculate numerically
several types of vortex structures in superfluid 3He-A. The calculations are
done in the Ginzburg-Landau region, but the method is applicable at all
temperatures. A phase diagram of vortices is constructed in the plane formed by
the magnetic field and the rotation velocity. The characteristics of the six
equilibrium vortex solutions are discussed. One of these, the locked vortex 3,
has not been considered in the literature before. The vortex sheet forms the
equilibrium state of rotating 3He-A at rotation velocities exceeding 2.6 rad/s.
The results are in qualitative agreement with experiments.Comment: 13 pages, 7 figures,
http://boojum.hut.fi/research/theory/diagram.htm
Nodes of the Gap Function and Anomalies in Thermodynamic Properties of Superfluid He
Departures of thermodynamic properties of three-dimensional superfluid He
from the predictions of BCS theory are analyzed. Attention is focused on
deviations of the ratios and
from their BCS values, where is the pairing gap at zero
temperature, is the critical temperature, and and are the
superfluid and normal specific heats. We attribute these deviations to the
momentum dependence of the gap function , which becomes well
pronounced when this function has a pair of nodes lying on either side of the
Fermi surface. We demonstrate that such a situation arises if the P-wave
pairing interaction , evaluated at the Fermi surface, has a sign
opposite to that anticipated in BCS theory. Taking account of the momentum
structure of the gap function, we derive a closed relation between the two
ratios that contains no adjustable parameters and agrees with the experimental
data. Some important features of the effective pairing interaction are inferred
from the analysis.Comment: 17 pages, 4 figure
Unconventional Vortices and Phase Transitions in Rapidly Rotating Superfluid ^{3}He
This paper studies vortex-lattice phases of rapidly rotating superfluid ^3He
based on the Ginzburg-Landau free-energy functional. To identify stable phases
in the p-Omega plane (p: pressure; Omega: angular velocity), the functional is
minimized with the Landau-level expansion method using up to 3000 Landau
levels. This system can sustain various exotic vortices by either (i) shifting
vortex cores among different components or (ii) filling in cores with
components not used in the bulk. In addition, the phase near the upper critical
angular velocity Omega_{c2} is neither the A nor B phases, but the polar state
with the smallest superfluid density as already shown by Schopohl. Thus,
multiple phases are anticipated to exist in the p-Omega plane. Six different
phases are found in the present calculation performed over 0.0001 Omega_{c2} <=
Omega <= Omega_{c2}, where Omega_{c2} is of order (1- T/T_c) times 10^{7}
rad/s. It is shown that the double-core vortex experimentally found in the B
phase originates from the conventional hexagonal lattice of the polar state
near Omega_{c2} via (i) a phase composed of interpenetrating polar and
Scharnberg-Klemm sublattices; (ii) the A-phase mixed-twist lattice with polar
cores; (iii) the normal-core lattice found in the isolated-vortex calculation
by Ohmi, Tsuneto, and Fujita; and (iv) the A-phase-core vortex discovered in
another isolated-vortex calculation by Salomaa and Volovik. It is predicted
that the double-core vortex will disappear completely in the experimental p-T
phase diagram to be replaced by the A-phase-core vortex for Omega >~ 10^{3} ~
10^{4} rad/s. C programs to minimize a single-component Ginzburg-Landau
functional are available at {http://phys.sci.hokudai.ac.jp/~kita/index-e.html}.Comment: 13 pages, 9 figure
The Interspersed Spin Boson Lattice Model
We describe a family of lattice models that support a new class of quantum
magnetism characterized by correlated spin and bosonic ordering [Phys. Rev.
Lett. 112, 180405 (2014)]. We explore the full phase diagram of the model using
Matrix-Product-State methods. Guided by these numerical results, we describe a
modified variational ansatz to improve our analytic description of the
groundstate at low boson frequencies. Additionally, we introduce an
experimental protocol capable of inferring the low-energy excitations of the
system by means of Fano scattering spectroscopy. Finally, we discuss the
implementation and characterization of this model with current circuit-QED
technology.Comment: Submitted to EPJ ST issue on "Novel Quantum Phases and Mesoscopic
Physics in Quantum Gases
A Theory for High- Superconductors Considering Inhomogeneous Charge Distribution
We propose a general theory for the critical and pseudogap
temperature dependence on the doping concentration for high- oxides,
taking into account the charge inhomogeneities in the planes. The well
measured experimental inhomogeneous charge density in a given compound is
assumed to produce a spatial distribution of local . These differences
in the local charge concentration is assumed to yield insulator and metallic
regions, possibly in a stripe morphology. In the metallic region, the
inhomogeneous charge density yields also spatial distributions of
superconducting critical temperatures and zero temperature gap
. For a given sample, the measured onset of vanishing gap
temperature is identified as the pseudogap temperature, that is, , which
is the maximum of all . Below , due to the distribution of
's, there are some superconducting regions surrounded by insulator or
metallic medium. The transition to a superconducting state corresponds to the
percolation threshold among the superconducting regions with different
's. To model the charge inhomogeneities we use a double branched
Poisson-Gaussian distribution. To make definite calculations and compare with
the experimental results, we derive phase diagrams for the BSCO, LSCO and YBCO
families, with a mean field theory for superconductivity using an extended
Hubbard Hamiltonian. We show also that this novel approach provides new
insights on several experimental features of high- oxides.Comment: 7 pages, 5 eps figures, corrected typo
Optical symmetries and anisotropic transport in high-Tc superconductors
A simple symmetry analysis of in-plane and out-of-plane transport in a family
of high temperature superconductors is presented. It is shown that generalized
scaling relations exist between the low frequency electronic Raman response and
the low frequency in-plane and out-of-plane conductivities in both the normal
and superconducting states of the cuprates. Specifically, for both the normal
and superconducting state, the temperature dependence of the low frequency
Raman slope scales with the axis conductivity, while the
Raman slope scales with the in-plane conductivity. Comparison with experiments
in the normal state of Bi-2212 and Y-123 imply that the nodal transport is
largely doping independent and metallic, while transport near the BZ axes is
governed by a quantum critical point near doping holes per
CuO plaquette. Important differences for La-214 are discussed. It is also
shown that the axis conductivity rise for is a consequence of
partial conservation of in-plane momentum for out-of-plane transport.Comment: 16 pages, 8 Figures (3 pages added, new discussion on pseudogap and
charge ordering in La214
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