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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. Source


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. Source


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. Source


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. Source


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. Source

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