362 research outputs found
Solitons: from Charge Density Waves to FFLO in superconductors
This short review aims to summarize on "What the Charge Density Waves can
tell to other inhomogeneous states in strongly correlated systems, particularly
to spin-polarized superconductors". We shall update on expanding observations
of solitons in quasi 1D CDW conductors and link them to the growing information
and demands related to inhomogeneous spin-polarized states in superconductors.
The related theory, existent or awaited for, stretches from solitons in 1D
models to vortex-like elementary excitations in 2D,3D ordered incommensurate
CDWs and superconductors.Comment: After presentations given at the conferences STRIPES 2008 and ECRYS
200
Electrodynamics of Josephson vortex lattice in high-temperature superconductors
We studied response of the Josephson vortex lattice in layered
superconductors to the high-frequency c-axis electric field. We found a simple
relation connecting the dynamic dielectric constant with the perturbation of
the superconducting phase, induced by oscillating electric field. Numerically
solving equations for the oscillating phases, we computed the frequency
dependences of the loss function at different magnetic fields, including
regions of both dilute and dense Josephson vortex lattices. The overall
behavior is mainly determined by the c-axis and in-plane dissipation
parameters, which is inversely proportional to the anisotropy. The cases of
weak and strong dissipation are realized in
and underdoped correspondingly. The main feature of the response is the
Josephson-plasma-resonance peak. In the weak-dissipation case additional
satellites appear in the dilute regime mostly in the higher-frequency region
due to excitation of the plasma modes with the wave vectors set by the lattice
structure. In the dense-lattice limit the plasma peak moves to higher frequency
and its intensity rapidly decreases, in agreement with experiment and
analytical theory. Behavior of the loss function at low frequencies is well
described by the phenomenological theory of vortex oscillations. In the case of
very strong in-plane dissipation an additional peak in the loss function
appears below the plasma frequency. Such peak has been observed experimentally
in underdoped . It is caused by frequency
dependence of in-plane contribution to losses rather then a definite mode of
phase oscillations.Comment: 10 pages, 7 figures, to be published in Phys.Rev.B, supplementary
animations of oscillating local electric field can be found at
http://mti.msd.anl.gov/homepages/koshelev/projects/JPRinJVL/Nz2vc0_32vab6_0Anim.ht
Collective responses of Bi-2212 stacked junction to 100 GHz microwave radiation under magnetic field oriented along the c-axis
We studied a response of Bi-2212 mesa type structures to 100 GHz microwave
radiation. We found that applying magnetic field of about 0.1 T across the
layers enables to observe collective Shapiro step response corresponding to a
synchronization of all 50 intrinsic Josephson junctions (IJJ) of the mesa. At
high microwave power we observed up to 10th harmonics of the fundamental
Shapiro step. Besides, we found microwave induced flux-flow step position of
which is proportional to the square root of microwave power and that can exceed
at high enough powers 1 THz operating frequency of IJJ oscillations.Comment: 11 pages including 5 figures, accepted for publication in JETP
Letter
Interlayer tunneling spectroscopy of graphite at high magnetic field oriented parallel to the layers
Interlayer tunneling in graphite mesa-type structures is studied at a strong
in-plane magnetic field up to 55 T and low temperature K. The
tunneling spectrum vs. has a pronounced peak at a finite voltage
. The peak position increases linearly with . To explain the
experiment, we develop a theoretical model of graphite in the crossed electric
and magnetic fields. When the fields satisfy the resonant condition
, where is the velocity of the two-dimensional Dirac electrons in
graphene, the wave functions delocalize and give rise to the peak in the
tunneling spectrum observed in the experiment.Comment: 6 pages, 6 figures; corresponds to the published version in Eur.
Phys. J. Special Topics, Proceedings of the IMPACT conference 2012,
http://lptms.u-psud.fr/impact2012
Subgap tunneling through channels of polarons and bipolarons in chain conductors
We suggest a theory of internal coherent tunneling in the pseudogap region
where the applied voltage is below the free electron gap. We consider quasi 1D
systems where the gap is originated by a lattice dimerization like in
polyacethylene, as well as low symmetry 1D semiconductors. Results may be
applied to several types of conjugated polymers, to semiconducting nanotubes
and to quantum wires of semiconductors. The approach may be generalized to
tunneling in strongly correlated systems showing the pseudogap effect, like the
family of High Tc materials in the undoped limit. We demonstrate the evolution
of tunneling current-voltage characteristics from smearing the free electron
gap down to threshold for tunneling of polarons and further down to the region
of bi-electronic tunneling via bipolarons or kink pairs.Comment: 14 pages, 8 postscript figure
Evaporation and growth of crystals - propagation of step density compression waves at vicinal surfaces
We studied the step dynamics during crystal sublimation and growth in the
limit of fast surface diffusion and slow kinetics of atom attachment-detachment
at the steps. For this limit we formulate a model free of the quasi-static
approximation in the calculation of the adatom concentration on the terraces at
the crystal surface. Such a model provides a relatively simple way to study the
linear stability of a step train in a presence of step-step repulsion and an
absence of destabilizing factors (as Schwoebel effect, surface electromigration
etc.). The central result is that a critical velocity of the steps in the train
exists which separates the stability and instability regimes. When the step
velocity exceeds its critical value the plot of these trajectories manifests
clear space and time periodicity (step density compression waves propagate on
the vicinal surface). This ordered motion of the steps is preceded by a
relatively short transition period of disordered step dynamics.Comment: 18 pages, 6 figure
Giant microwave-induced -periodic magnetoresistance oscillations in a two-dimensional electron gas with a bridged-gate tunnel point contact
We have studied the magnetoresistance of the quantum point contact fabricated
on the high mobility two-dimensional electron gas (2DEG) exposed to microwave
irradiation. The resistance reveals giant -periodic oscillations with the
relative amplitude of up to \% resulting from the propagation
and interference of the edge magnetoplasmons (EMPs) in the sample. This giant
photoconductance is attributed to the considerably large local electron density
modulation in the vicinity of the point contact. We have also analyzed the
oscillation periods of the resistance oscillations and, comparing
the data with the EMP theory, extracted the EMP interference length . We
have found that the length substantially exceeds the distance between the
contact leads but rather corresponds to the distance between metallic contact
pads measured along the edge of the 2DEG. This resolves existing controversy in
the literature and should help to properly design highly sensitive microwave
and terahertz spectrometers based on the discussed effect.Comment: 5 pages, 5 figure
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