Quantitative investigation of the deHaas-vanAlphen effect in the superconducting state

The de Haas-van Alphen effect in the vortex state of the type-II superconductors 2H-NbSe2 and V3Si is studied. We discuss the experimental and theoretical considerations pertaining to the observation of such oscillations. Macroscopic pinning of the flux lattice cannot explain the observed attenuation of quantum oscillations in the mixed state. A critical comparison of our measurements with the various microscopic theoretical models describing this phenomenon is made. We show how orientation-dependent de Haas-van Alphen data may be analyzed in a model-dependent way to yield the variation of the superconducting gap over the Fermi surface.