288 research outputs found
Nanopattern-stimulated superconductor-insulator transition in thin TiN films
We present the results of the comparative study of the influence of disorder
on transport properties in continuous and nanoperforated TiN films. We show
that nanopatterning turns a thin TiN film into an array of superconducting weak
links and stimulates both, the disorder- and magnetic field-driven
superconductor-to-insulator transitions, pushing them to lower degree of
disorder. We find that nanopatterning enhances the role of the two-dimensional
Coulomb interaction in the system transforming the originally insulating film
into a more pronounced insulator. We observe magnetoresistance oscillations
reflecting collective behaviour of the multiconnected nanopatterned
superconducting film in the wide range of temperatures and uncover the physical
mechanism of these oscillations as phase slips in superconducting weak link
network.Comment: 6 pages, 4 figure
Anomalous asymmetry of magnetoresistance in NbSe single crystals
A pronounced asymmetry of magnetoresistance with respect to the magnetic
field direction is observed for NbSe crystals placed in a magnetic field
perpendicular to their conducting planes. It is shown that the effect persists
in a wide temperature range and manifests itself starting from a certain
magnetic induction value , which at K corresponds to the
transition to the quantum limit, i.to the state where the Landay level
splitting exceeds the temperature.Comment: 4 pages, 6 figures, to be appeared in JETP Let
Interaction of the Electromagnetic p-Waves with Thin Metal Films
For the first time it is shown that for thin metallic films thickness of
which not exceed thickness of skin-layer, the problem allows analytical
solution for arbitrary boundary value problems. The analysis of dependence of
coefficients of transmission, reflection and absorbtion on angle incidence,
thickness of films and coefficient of specular reflection is carried out.Comment: 15 pages, 9 figure
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
From Discrete Hopping to Continuum Modeling on Vicinal Surfaces with Applications to Si(001) Electromigration
Coarse-grained modeling of dynamics on vicinal surfaces concentrates on the
diffusion of adatoms on terraces with boundary conditions at sharp steps, as
first studied by Burton, Cabrera and Frank (BCF). Recent electromigration
experiments on vicinal Si surfaces suggest the need for more general boundary
conditions in a BCF approach. We study a discrete 1D hopping model that takes
into account asymmetry in the hopping rates in the region around a step and the
finite probability of incorporation into the solid at the step site. By
expanding the continuous concentration field in a Taylor series evaluated at
discrete sites near the step, we relate the kinetic coefficients and
permeability rate in general sharp step models to the physically suggestive
parameters of the hopping models. In particular we find that both the kinetic
coefficients and permeability rate can be negative when diffusion is faster
near the step than on terraces. These ideas are used to provide an
understanding of recent electromigration experiment on Si(001) surfaces where
step bunching is induced by an electric field directed at various angles to the
steps.Comment: 10 pages, 4 figure
Suppressed superconductivity in ultrathin Mo2N films due to pair-breaking at the interface
A strong disorder characterized by a small product of the Fermi vector kF and
the electron mean free l drives superconductors towards insulating state. Such
disorder can be introduced by making the films very thin. Here, we present 3-nm
Mo2N film with k_F*l ~ 2 with a resistive superconducting transition
temperature Tc = 2 K heavily suppressed in comparison with the bulk Tc.
Superconducting density of states (DOS) with smeared gap-like peaks and in-gap
states, so called Dynes DOS, is observed by the low temperature tunneling
spectroscopy despite a sharp resistive transition. By scanning tunneling
microscope the spectral maps are obtained and related to the surface
topography. The maps show a spatial variation of the superconducting energy gap
on the order of 20 % which is not accidental but well correlates with the
surface corrugation: protrusions reveal larger gap, smaller spectral smearing
and smaller in-gap states. In agreement with our previous measurements on
ultrathin MoC films we suggest that the film-substrate interface introducing
the local pair-breaking is responsible for the observed effects and generally
for the suppression of the superconductivity in these ultrathin films.Comment: Manuscript with 3 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
Interaction of Electromagnetic S-Wave with a Metal Film Located Between Two Dielectric Mediums
Generalization of the theory of interaction of electromagnetic S-wave with a
metal film on a case of the film concluded between two dielectric environments
is developed.Comment: 13 pages, 10 figure
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