Session P5 - Vortices in Superconductors.
INVITED session, Wednesday morning, March 05
Ballroom F, Austin Convention Center
An interaction of vortices in superconductors with acoustic waves is very unusual. In a clean sample helicon waves interact with the transverse sound resulting in the additional sound attenuation [1]. Interaction of a vortex lattice with ultrasound may produce the acoustic Faraday effect and nonstationary magnetic field, acting on vortices, may generate ultrasonic waves [2]. Vortices interact with acoustic waves either through pinning centers or by the mechanisms which exist even in normal metals: electromagnetic forces or forces mediated by impurities. When the velocity of vortices exceeds the velocity of sound, each vortex produces the Cherenkov radiation of sound waves. The velocity field of lattice ions is localized on the Cherenkov cone, but the forces, acting on the lattice, are localized on vortex positions. When the Cherenkov cone coincides with certain directions in the moving vortex lattice, the dissipation exhibits maxima. Since the direction of the Cherenkov cone is determined by the vortex velocity (electric field) one can expect a series of resonant peaks in the current-voltage characteristic at particular values of electric field [3]. A radiation-friction component of the vortex dissipation also peaks at values of vortex velocity where there are phonons in the Brillouin zone of the crystal with matching phase and group velocities (the van Hove condition) [4]. Thus, besides the Crenkov peaks, also the van Hove peaks are expected in the current-voltage characteristic of the vortex state. [1] G. Blatter and B. Ivlev, Phys.Rev. B 52, 4588 (1995); [2] D. Dominguez, L. Bulaevskii, B. Ivlev, M. Maley, and A. Bishop, Phys.Rev.Lett. 74, 2579 (1995); [3] B. Ivlev, S. Mejia Rosales, and M.Kunchur, Phys.Rev. B 60, 12419 (1999); [4] B. Ivlev, M. Kunchur, and S. Mejia Rosales, Phys.Rev. B 64, 024508 (2001)