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Barash Y.S.,RAS Institute of Solid State Physics
Physical Review B - Condensed Matter and Materials Physics | Year: 2017

Superconductivity is shown to be completely destroyed in thin mesoscopic or nanoscopic rings closed by the junction with a noticeable interfacial pair breaking and/or a Josephson coupling, if a ring's radius r is less than the minimum radius rmin. The quantity rmin depends on the phase difference χ across the junction, or on the magnetic flux that controls χ in the flux-biased ring. It also depends on the Josephson and interfacial effective coupling constants, and in particular, on whether the ring is closed by the 0 or the π junction. The current-phase relation is substantially modified when the ring's radius exceeds rmin for some of the phase difference values, or slightly goes beyond its maximum. The modified critical temperature Tc and the temperature-dependent supercurrent near Tc are identified here as functions of the ring's radius and the magnetic flux. © 2017 American Physical Society.

Barash Yu.S.,RAS Institute of Solid State Physics
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

It will be shown that a pronounced interfacial pair breaking can be identified in Josephson tunnel junctions provided the first j 1c and the second j 2c harmonics of the supercurrent, as well as the depairing current in the bulk j dp, are known. Namely, within the Ginzburg-Landau theory a strong interfacial pair breaking results in the relation j 2cj dp j1c2, while in standard junctions, with negligibly small pair breaking, the relation of opposite character takes place. © 2012 American Physical Society.

Barash Yu.S.,RAS Institute of Solid State Physics
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

In the junctions with a strong Josephson coupling and a pronounced interfacial pair breaking, the magnetic interference patterns of the Josephson current are shown to differ substantially from the standard Fraunhofer shape. The Fraunhofer pattern occurs when the Josephson coupling is weak. The narrow peak of the critical current, centered at the zero magnetic field, and the suppressed hills at finite field values are the characteristic features of the non-Fraunhofer magnetic field modulation of the critical current, obtained in this paper. © 2012 American Physical Society.

Dickmann S.,RAS Institute of Solid State Physics
Physical Review Letters | Year: 2013

Cyclotron spin-flip excitation in a ν=2 quantum Hall system, being separated from the ground state by a slightly smaller gap than the cyclotron energy and from upper magnetoplasma excitation by the Coulomb gap cannot relax in a purely electronic way except only with the emission of a shortwave acoustic phonon (k∼3×107/cm). As a result, relaxation in a modern wide-thickness quantum well occurs very slowly. We calculate the characteristic relaxation time to be ∼1 s. Extremely slow relaxation should allow the production of a considerable density of zero-momenta cyclotron spin-flip excitations in a very small phase volume, thus forming a highly coherent ensemble - the Bose-Einstein condensate. The condensate state can be controlled by short optical pulses (1 μs), switching it on and off. © 2013 American Physical Society.

Barash Yu.S.,RAS Institute of Solid State Physics
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Planar superconducting junctions with a large effective Josephson coupling constant and a pronounced interface pair breaking are shown to represent weak links with small critical currents and strongly anharmonic current-phase relations. The supercurrent near T c is described taking into account the interface pair breaking as well as the current depairing and the Josephson coupling-induced pair breaking of arbitrary strengths. An analytical expression for the anharmonic supercurrent, which is in excellent agreement with the numerical data presented, is obtained. In junctions with a large effective Josephson coupling constant and a pronounced interface pair breaking, the current-induced depairing is substantially enhanced in the vicinity of the interface thus having a crucial influence on the current-phase relation despite a small depairing in the bulk. © 2012 American Physical Society.

Gavrilov S.S.,RAS Institute of Solid State Physics
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

Based on the Gross-Pitaevskii equations, it is predicted that a repulsive interaction provides a way for a two-dimensional polariton condensate to accumulate energy in spite of dissipation under above-resonance optical pumping. The energy can be accumulated over a time much longer than the polariton lifetime, resulting in the state in which the blueshift of the polariton level compensates the mismatch of the pump frequency. The process starts when the field density reaches the parametric scattering threshold that is inversely proportional to the polariton lifetime. Although the increase in energy may be arbitrarily slow in the beginning, it is followed by a blowup. This scenario applies to the case of transitions between steady states in multistable cavity-polariton systems. There is a tradeoff between the latency of the transitions and the pump power. © 2014 American Physical Society.

Degtyareva V.F.,RAS Institute of Solid State Physics
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials | Year: 2014

A simple cubic structure with one atom in the unit cell found in compressed calcium is counterintuitive to the traditional view of a tendency towards densely packed structures with an increase in pressure. To understand this unusual transformation it is necessary to assume electron transfer from the outer core band to the valence band, and an increase of valence electron number for calcium from 2 to ∼3.5. This assumption is supported by the Fermi sphere-Brillouin zone interaction model that increases under compression. The recently found structure of Ca-VII with a tetragonal cell containing 32 atoms (tI32) is similar to that in the intermetallic compound In5Bi3 with 3.75 valence electrons per atom. Structural relations are analyzed in terms of electronic structure resemblance. Correlations of structure and physical properties of Ca are discussed. © 2014 International Union of Crystallography.

A comparative analysis of experimental data on electron transport in Si (100) MOSFETs in the region of high mobilities and strong electron-electron interaction is carried out. It is shown that electrons can be described by the model of a noninteracting gas with the renormalized mass and Lande factor, which allows experimentally verifiable predictions. © 2015, Pleiades Publishing, Inc.

Misochko O.V.,RAS Institute of Solid State Physics
Physics-Uspekhi | Year: 2013

We consider theoretical and experimental evidence for nonclassical states of a crystal lattice. Our primary goal is the critical analysis of recent experiments in which squeezed and entangled phonons are created and investigated. The quantum aspects of elastic deformation fields similar to nonclassical light fields are of interest for potential use in applied and fundamen- tal research, including quantum computing and testing various hypotheses in quantum physics. Copyright © 2013 John Wiley & Sons, Ltd.

Dolganov P.V.,RAS Institute of Solid State Physics
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

Density of photonic states ρ(ω), group vg, and phase vph velocity of light, and the dispersion relation between wave vector k, and frequency ω(k) were determined in a cholesteric photonic crystal. A highly sensitive method (measurement of rotation of the plane of polarization of light) was used to determine ρ(ω) in samples of different quality. In high-quality samples a drastic increase in ρ(ω) near the boundaries of the stop band and oscillations related to Pendellösung beatings are observed. In low-quality samples photonic properties are strongly modified. The maximal value of ρ(ω) is substantially smaller, and density of photonic states increases near the selective reflection band without oscillations in ρ(ω). Peculiarities of ρ(ω), vg, and ω(k) are discussed. Comparison of the experimental results with theory was performed. © 2015 American Physical Society.

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