Magnus force and acoustic Stewart-Tolman effect in type-II superconductors

Abstract

At zero magnetic field we have observed an electromagnetic radiation from superconductors subjected by a transverse elastic wave. This radiation has an inertial origin, and is a manifestation of the acoustic Stewart-Tolman effect. The effect is used for implementing a method of measurement of an effective Magnus force in type II superconductors. The method does not require the flux flow regime and allows to investigate this force for almost the whole range of the existence of the mixed state. We have studied behavior of the gyroscopic force in nonmagnetic borocarbides and Nb. It is found that in borocarbides the sign of the gyroscopic force in the mixed state is the same as in the normal state, and its value (counted for one vortex of unit length) has only a weak dependence on the magnetic field. In Nb the change of sign of the gyroscopic force under the transition from the normal to the mixed state is observed.

Transverse acousto-electric effect in superconductors

“…2 in Ref. [7]). This small change shows that, at least in the vicinity of the transition temperature, the normal and the superconducting currents are comparable, which is incompatible with the assumption of stationary ('clamped') normal electrons.…”

“…The standard time-dependent Ginzburg-Landau theory (TDGL), which contains the assumption of local equilibrium, and is formulated in the laboratory frame, is a powerful tool to study phenomena in the vicinity of the superconducting-normal phase transition. To study gyroscopes [1], gravitational wave antennae [2] and the interaction of the superconducting condensate with strong sound waves [3,4,5,6,7,8,9,10,11,12,13], where the atomic lattice is in motion, an extension to TDGL is needed to accommodate the dynamical system.…”

“…In particular, under the influence of the ultrasound wave, the inertial motion of normal electrons as well as superconducting electrons leads to nonzero bulk currents via the Tolman-Stewart effect. The oscillating current radiates electromagnetic waves [6,7] so that the superconductor exhibits nonzero acousto-electric effect.…”

“…Theoretical analysis of the acousto-electric field in superconductors has been performed assuming the fully superconducting state with no normal current [7]; the normal electrons are 'clamped' to the lattice [4,5,11,12]. Using this assumption, the TDGL theory of Verkin and Kulik [15] (originally developed for the case of steady rotation when normal currents are absent) can be used to study the acousto-electric field.…”

“…In the transverse wave the material experiences shear stress only, without compression. According to the experimental studies by Fil et al [7], the changes of potential and material parameters caused by shear deformations can be disregarded. To accommodate this non-equilibrium system, we use a modified version of TDGL theory based on a microscopic derivation [16].…”