3,783 research outputs found
Low- Phononic Thermal Conductivity in Superconductors with Line Nodes
The phonon contribution to the thermal conductivity at low temperature in
superconductors with line nodes is calculated assuming that scattering by both
nodal quasiparticles and the sample boundaries is significant. It is determined
that, within the regime in which the quasiparticles are in the universal limit
and the phonon attenuation is in the hydrodynamic limit, there exists a wide
temperature range over which the phonon thermal conductivity varies as .
This behaviour comes from the fact that transverse phonons propagating along
certain directions do not interact with nodal quasiparticles and is thus found
to be required by the symmetry of the crystal and the superconducting gap,
independent of the model used for the electron-phonon interaction. The
-dependence of the phonon thermal conductivity occurs over a well-defined
intermediate temperature range: at higher the temperature-dependence is
found to be linear while at lower the usual (boundary-limited)
behaviour is recovered. Results are compared to recent measurements of the
thermal conductivity of Tl2201, and are shown to be consistent with the data.Comment: 4 page
Multidimensional Pattern Formation Has an Infinite Number of Constants of Motion
Extending our previous work on 2D growth for the Laplace equation we study
here {\it multidimensional} growth for {\it arbitrary elliptic} equations,
describing inhomogeneous and anisotropic pattern formations processes. We find
that these nonlinear processes are governed by an infinite number of
conservation laws. Moreover, in many cases {\it all dynamics of the interface
can be reduced to the linear time--dependence of only one ``moment" }
which corresponds to the changing volume while {\it all higher moments, ,
are constant in time. These moments have a purely geometrical nature}, and thus
carry information about the moving shape. These conserved quantities (eqs.~(7)
and (8) of this article) are interpreted as coefficients of the multipole
expansion of the Newtonian potential created by the mass uniformly occupying
the domain enclosing the moving interface. Thus the question of how to recover
the moving shape using these conserved quantities is reduced to the classical
inverse potential problem of reconstructing the shape of a body from its
exterior gravitational potential. Our results also suggest the possibility of
controlling a moving interface by appropriate varying the location and strength
of sources and sinks.Comment: CYCLER Paper 93feb00
Classical phase fluctuations in d-wave superconductors
We study the effects of low-energy nodal quasiparticles on the classical
phase fluctuations in a two-dimensional d-wave superconductor. The
singularities of the phase-only action at T\to 0 are removed in the presence of
disorder, which justifies using an extended classical XY-model to describe
phase fluctuations at low temperatures.Comment: 14 pages, brief review for Mod. Phys. Lett.
Superconductivity in ferromagnetic metals and in compounds without inversion centre
The symmetry properties and the general overview of the superconductivity
theory in the itinerant ferromagnets and in materials without space parity are
presented. The basic notions of unconventional superconductivity are introduced
in broad context of multiband superconductivity which is inherent property of
ferromagnetic metals or metals without centre of inversion.Comment: 38 pages, no figure
Charged-Surface Instability Development in Liquid Helium; Exact Solutions
The nonlinear dynamics of charged-surface instability development was
investigated for liquid helium far above the critical point. It is found that,
if the surface charge completely screens the field above the surface, the
equations of three-dimensional (3D) potential motion of a fluid are reduced to
the well-known equations describing the 3D Laplacian growth process. The
integrability of these equations in 2D geometry allows the analytic description
of the free-surface evolution up to the formation of cuspidal singularities at
the surface.Comment: latex, 5 pages, no figure
A note on the extension of the polar decomposition for the multidimensional Burgers equation
It is shown that the generalizations to more than one space dimension of the
pole decomposition for the Burgers equation with finite viscosity and no force
are of the form u = -2 viscosity grad log P, where the P's are explicitly known
algebraic (or trigonometric) polynomials in the space variables with polynomial
(or exponential) dependence on time. Such solutions have polar singularities on
complex algebraic varieties.Comment: 3 pages; minor formatting and typos corrected. Submitted to Phys.
Rev. E (Rapid Comm.
Integrable Structure of Interface Dynamics
We establish the equivalence of a 2D contour dynamics to the dispersionless
limit of the integrable Toda hierarchy constrained by a string equation.
Remarkably, the same hierarchy underlies 2D quantum gravity.Comment: 5 pages, no figures, submitted to Phys. Rev. Lett, typos correcte
Viscous fingering and a shape of an electronic droplet in the Quantum Hall regime
We show that the semiclassical dynamics of an electronic droplet confined in
the plane in a quantizing inhomogeneous magnetic field in the regime when the
electrostatic interaction is negligible is similar to viscous (Saffman-Taylor)
fingering on the interface between two fluids with different viscosities
confined in a Hele-Shaw cell. Both phenomena are described by the same
equations with scales differing by a factor of up to . We also report
the quasiclassical wave function of the droplet in an inhomogeneous magnetic
field.Comment: 4 pages, 1 eps figure include
Gap structure in noncentrosymmetric superconductors
Gap structure in noncentrosymmetric superconductors with spin-orbit band
splitting is studied using a microscopic model of pairing mediated by phonons
and/or spin fluctuations. The general form of pairing interaction in the band
representation is derived, which includes both the intraband and interband
pairing terms. In the case of isotropic interaction (in particular, for a
BCS-contact interaction), the interband pairing terms vanish identically at any
magnitude of the band splitting. The effects of pairing interaction anisotropy
are analyzed in detail for a metal of cubic symmetry with strong spin-orbit
coupling. It is shown that if phonons are dominant then the gaps in two bands
are isotropic, nodeless, and have in general different amplitudes. Applications
to the Li_2(Pd_{1-x},Pt_x)_3B family of noncentrosymmetric superconductors are
discussed.Comment: 9 pages; minor corrections, published versio
NMR relaxation time in a clean two-band superconductor
We study the spin-lattice relaxation rate of nuclear magnetic resonance in a
two-band superconductor. Both conventional and unconventional pairing
symmetries for an arbitrary band structure in the clean limit are considered.
The importance of the inter-band interference effects is emphasized. The
calculations in the conventional case with two isotropic gaps are performed
using a two-band generalization of Eliashberg theory.Comment: 9 pages, 3 figure
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