24 research outputs found
On details of the thermodynamical derivation of the Ginsburg--Landau equations
We examine the procedure of thermodynamical derivation of the
Ginsburg--Landau equation for current, which is given unclear and contradictory
interpretations in existing textbooks. We clarify all steps of this procedure
and find as a consequence a limitation on the validity range of the
thermodynamic Ginsburg--Landau theory, which does not seem to be explicitely
stated up to now: we conclude that the thermodynamic theory is applicable only
to a superconducting specimen that is not a part of an external
current-carrying loop.Comment: 11 pages. Accepted for publication in 'Superconductor Science and
Technology
A super-Ohmic energy absorption in driven quantum chaotic systems
We consider energy absorption by driven chaotic systems of the symplectic
symmetry class. According to our analytical perturbative calculation, at the
initial stage of evolution the energy growth with time can be faster than
linear. This appears to be an analog of weak anti-localization in disordered
systems with spin-orbit interaction. Our analytical result is also confirmed by
numerical calculations for the symplectic quantum kicked rotor.Comment: 4 pages, 2 figure
Switchable collective pinning of flux quanta using magnetic vortex arrays
We constructed a superconducting/ferromagnetic hybrid system in which the
ordering of the pinning potential landscape for flux quanta can be manipulated.
Flux pinning is induced by an array of magnetic nanodots in the magnetic vortex
state, and controlled by the magnetic history. This allows switching on and off
the collective pinning of the flux-lattice. In addition, we observed
field-induced superconductivity that originates from the annihilation of flux
quanta induced by the stray fields from the magnetic vortices.Comment: PDF file 18 pages including 5 figures, accepted for publication in
Phys. Rev.
Metastable bound state of a pair of two-dimensional spatially separated electrons in anti-parallel magnetic fields
We propose a new mechanism for binding of two equally charged carriers in a
double-layer system subjected by a magnetic field of a special form. A field
configuration for which the magnetic fields in adjacent layers are equal in
magnitude and opposite in direction is considered. In such a field an
additional integral of motion - the momentum of the pair P arises. For the case
when in one layer the carrier is in the zero (n=0) Landau level while in the
other layer - in the first (n=1) Landau level the dependence of the energy of
the pair on its momentum E(P} is found. This dependence turns out to be
nonmonotonic one : a local maximum and a local minimum appears, indicating the
emergence of a metastable bound state of two carrier with the same sign of
electrical charge.Comment: 7 page
Giant magnetooscillations of the Josephson current
Josephson current flowing through an antiferromagnetic metallic barrier is studied. We consider the most interesting case of the spin-valve structure when the barrier is formed by ferromagnetic layers ordered antiferromagnetically in the direction perpendicular to the current. The most remarkable feature is an appearance of giant magnetooscillations of the current amplitude
De Haas-van Alphen effect and superconductivity
The problem of the robust de Haas-van Alphen oscillations seen experimentally in mixed superconducting state is discussed. The new threshold mechanism is suggested to explain persistence of the quantum oscillations deep in the superconducting state
Recommended from our members
Theoretical studies of magnetic systems. Final report, August 1, 1994--November 30, 1997
During the grant period the authors have studied five areas of research: (1) low dimensional ferrimagnets; (2) lattice effects in the mixed valence problem; (3) spin compensation in the one dimensional Kondo lattice; (4) the interaction of quasi particles in short coherence length superconductors; and (5) novel effects in angle resolved photoemission spectra from nearly antiferromagnetic materials. Progress in each area is summarized