376 research outputs found
Abrikosov vortex escape from a columnar defect as a topological electronic transition in vortex core
We study microscopic scenario of vortex escape from a columnar defect under
the influence of a transport current. For defect radii smaller than the
superconducting coherence length the depinning process is shown to be a
consequence of two subsequent topological electronic transitions in a trapped
vortex core. The first transition at a critical current is associated
with the opening of Fermi surface segments corresponding to the creation of a
vortex--antivortex pair bound to the defect. The second transition at a certain
current is caused by merging of different Fermi surface segments,
which accompanies the formation of a freely moving vortex.Comment: 5 pages, 4 figure
Theory of vortex lattice effects on STM spectra in d-wave superconductors
Theory of scanning tunneling spectroscopy of low energy quasiparticle (QP)
states in vortex lattices of d-wave superconductors is developed taking account
of the effects caused by an extremely large extension of QP wavefunctions in
the nodal directions and the band structure in the QP spectrum. The oscillatory
structures in STM spectra, which correspond to van Hove singularities are
analysed. Theoretical calculations carried out for finite temperatures and
scattering rates are compared with recent experimental data for high
temperature cuprates.Comment: 4 pages, 3 eps figures, M2S-HTSC-VI conference paper, using Elsevier
style espcrc2.st
Resonance energy and charge pumping through quantum SINIS contacts
We propose a mechanism of quantum pumping mediated by the spectral flow in a
voltage-biased SINIS quantum junction and realized via the sequential closing
of the minigaps in the energy spectrum in resonance with the Josephson
frequency. We show that the dc current exhibits giant peaks at rational
voltages
DNA conformational dynamics in the presence of catanionic mixtures
DNA conformational behavior in the presence of non-stoichiometric mixtures of two oppositely charged surfactants, cetyltrimethylammonium bromide and sodium octyl sulfate, was directly visualized in an aqueous solution with the use of a fluorescence microscopy technique. It was found that in the presence of cationic-rich catanionic mixtures, DNA molecules exhibit a conformational transition from elongated coil to compact globule states. Moreover, if the catanionic mixtures form positively charged vesicles, DNA is adsorbed onto the surface of the vesicles in a collapsed globular form. When anionic-rich catanionic mixtures are present in the solution, no change in the DNA conformational behavior was detected. Cryogenic transmission electron microscopy, as well as measurements of translational diffusion coefficients of individual DNA chains, supported our optical microscopy observations.http://www.sciencedirect.com/science/article/B6T36-3WRB313-V/1/07d45ede3443f93c49fe5d72c57fdfa
Local density of states around single vortices and vortex pairs: effect of boundaries and hybridization of vortex core states
The profiles of local density of states (LDOS) around different vortex
configurations in mesoscopic superconductors are studied taking account of the
interference of quasiparticle waves experiencing Andreev reflection within the
vortex cores and normal reflection at the boundaries or defects. For subgap
energy levels these interference effects reveal themselves in a nontrivial
dependence of the positions of the LDOS peaks on the intervortex distance and
sample size: the peak positions generally do not coincide with the
superconducting phase singularity points. The LDOS profiles are calculated for
three generic examples: (i) vortex-vortex pair; (ii) vortex positioned near a
flat boundary; (iii) vortex positioned in the center of a superconducting disk.
The resulting evolution of the Andreev interference patterns could be
observable by scanning tunneling spectroscopy techniques.Comment: 9 pages, 6 figure
Multiple Vortex Cores in 2D Electronic Systems with Proximity Induced Superconductivity
The structure of a proximity induced vortex core in a two-dimensional (2D)
metallic layer covering a superconducting half-space is calculated. We predict
formation of a multiple vortex core characterized by two-scale behavior of the
local density of states (LDOS). For coherent tunnelling between the 2D layer
and the bulk superconductor, the spectrum has two subgap branches while for
incoherent tunnelling only one of them remains. The resulting splitting of the
zero-bias anomaly and the multiple peak structure in the LDOS should be visible
in the tunnelling spectroscopy experiments.Comment: 13 pages, 4 figure
Single-electron transport through the vortex core levels in clean superconductors
We develop a microscopic theory of single-electron transport in N-S-N hybrid
structures in the presence of applied magnetic field introducing vortex lines
in a superconductor layer. We show that vortex cores in a thick and clean
superconducting layer are similar to mesoscopic conducting channels where the
bound core states play the role of transverse modes. The transport through not
very thick layers is governed by another mechanism, namely by resonance
tunneling via vortex core levels. We apply our method to calculation of the
thermal conductance along the magnetic field.Comment: 4 pages, 1 figur
A new extended matrix KP hierarchy and its solutions
With the square eigenfunctions symmetry constraint, we introduce a new
extended matrix KP hierarchy and its Lax representation from the matrix KP
hierarchy by adding a new flow. The extended KP hierarchy contains two
time series and and eigenfunctions and adjoint
eigenfunctions as components. The extended matrix KP hierarchy and its
-reduction and reduction include two types of matrix KP hierarchy
with self-consistent sources and two types of (1+1)-dimensional reduced matrix
KP hierarchy with self-consistent sources. In particular, the first type and
second type of the 2+1 AKNS equation and the Davey-Stewartson equation with
self-consistent sources are deduced from the extended matrix KP hierarchy. The
generalized dressing approach for solving the extended matrix KP hierarchy is
proposed and some solutions are presented. The soliton solutions of two types
of 2+1-dimensional AKNS equation with self-consistent sources and two types of
Davey-Stewartson equation with self-consistent sources are studied.Comment: 17 page
Binding of molecules to DNA and other semiflexible polymers
A theory is presented for the binding of small molecules such as surfactants
to semiflexible polymers. The persistence length is assumed to be large
compared to the monomer size but much smaller than the total chain length. Such
polymers (e.g. DNA) represent an intermediate case between flexible polymers
and stiff, rod-like ones, whose association with small molecules was previously
studied. The chains are not flexible enough to actively participate in the
self-assembly, yet their fluctuations induce long-range attractive interactions
between bound molecules. In cases where the binding significantly affects the
local chain stiffness, those interactions lead to a very sharp, cooperative
association. This scenario is of relevance to the association of DNA with
surfactants and compact proteins such as RecA. External tension exerted on the
chain is found to significantly modify the binding by suppressing the
fluctuation-induced interaction.Comment: 15 pages, 7 figures, RevTex, the published versio
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
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