Coherence in the quasiparticle scattering by the vortex lattice in pure type-II superconductors

The effect of quasiparticle (QP) scattering by the vortex lattice on the de Haas-van Alphen (dHvA) oscillations in a pure type-II superconductor is investigated within a mean-field asymptotic perturbation theory. Using a two-dimensional (2D) electron-gas model it is shown that, due to a strict phase coherence in the many particle correlation functions, the scattering effect in the asymptotic limit (√E_F/ħω_c≫1) is much weaker than what is predicted by the random vortex-lattice model proposed by Maki and Stephen, which destroys this coherence. The coherent many particle configuration is a collinear array of many particle coordinates, localized within a spatial region with size of the order of the magnetic length. The amplitude of the magnetization oscillations is sharply damped just below H_c2 because of strong 180° out of phase magnetic oscillations in the superconducting condensation energy, which tend to cancel the normal electron oscillations. Within the ideal 2D model used it is found, however, that because of the relative smallness of the quartic and higher order terms in the expansion, the oscillations amplitude at lower fields does not really damp to zero, but only reverses sign and remains virtually undamped well below H_c2. This conclusion may be changed if disorder in the vortex lattice, or vortex line motion is taken into account. The reduced QP scattering effect may be responsible for the apparent crossover from a strong damping of the dHvA oscillations just below H_c2 to a weaker damping at lower fields observed experimentally in several 3D superconductors.