Electron-phonon heat transfer in giant vortex states

We examine energy relaxation of nonequilibrium quasiparticles (QPs) in different vortex configurations in "dirty" s-wave superconductors (SCs). The heat flow from the electronic subsystem to phonons in a mesoscopic SC disk with a radius of the order of several coherence lengths is calculated both in the Meissner and in the giant vortex states using the Usadel approach. The recombination process is shown to be strongly affected by interplay of the subgap states, located in the vortex core and in the region at the sample edge where the spectral gap Eg is reduced by the Meissner currents. In order to uncover the physical origin of the results, we develop a semiquantitative analytical approximation based on the combination of homogeneous solutions of Usadel equations in Meissner and vortex states of a mesoscopic SC disk and analytically calculate the corresponding spatially resolved electron-phonon heat rates. Our approach provides important information about nonequilibrium QPs cooling by the magnetic field-induced traps in various mesoscopic SC devices

Whispering Vortices

Experiments indicating the excitation of whispering gallery type electromagnetic modes by a vortex moving in an annular Josephson junction are reported. At relativistic velocities the Josephson vortex interacts with the modes of the superconducting stripline resonator giving rise to novel resonances on the current-voltage characteristic of the junction. The experimental data are in good agreement with analysis and numerical calculations based on the two-dimensional sine--Gordon model.Comment: 5 pages, 5 figures, text shortened to fit 4 pages, correction of typo

Dynamics and transformations of Josephson vortex lattice in layered superconductors

We consider dynamics of Josephson vortex lattice in layered superconductors with magnetic, charge (electrostatic) and charge-imbalance (quasiparticle) interactions between interlayer Josephson junctions taken into account. The macroscopic dynamical equations for interlayer Josephson phase differences, intralayer charge and electron-hole imbalance are obtained and used for numerical simulations. Different transformations of the vortex lattice structure are observed. It is shown that the additional dissipation due to the charge imbalance relaxation leads to the stability of triangular lattice.Comment: 9 pages, 3 eps figures, to be published in Phys. Rev.

Adaptive techniques of the wavefield formation in random-inhomogeneous multimode propagation channels by the use of large arrays

We address the source array synthesis problem in a random propagation channel under the different optimization criteria specified for the remote receiving array, namely, the criteria of (i) the output SNR and (ii) the array gain. For the first step, we discuss the optimal schemes for the source excitation and array beamforming by using a general technique of the eigenvalue-eigenvector expansion associated with the normal-mode model of long-range signal propagation in a channel. Then, we develop an adaptive approach to the source array synthesis which is shown to be an iterative correction of the sources excitation coefficients depending on the signal coherence, the receiving array arrangement in a channel, and also on the modal spectrum of the ambient noise interference. Computer simulation is performed for the vertical source and receiving arrays in random-inhomogeneous environments typical for sound propagation in shallow-water channels from the Barents Sea. The results exhibit distinctly a rather high efficiency of the adaptive synthesis algorithms for various sets of the source and environmental parameters including the signal frequency, distance, vertical locations of the sources and receivers