Magnetic oscillations and quasiparticle band structure in the mixed state of type-II superconductors.

We consider magnetic oscillations due to Landau quantization in the mixed state of type-II superconductors. Our work is based on a previously developed formalism which allows the mean-field gap equations of the Abrikosov state to be conveniently solved in a Landau level representation. We find that the quasiparticle band structure changes qualitatively when the pairing selfenergy becomes comparable to the Landau level separation. For small pairing self-energies, Landau level mixing due to the superconducting order is weak and magnetic oscillations survive in the superconducting state although they are damped. We find that the width of the quasiparticle Landau levels in this regime varies approximately as ∆0n −1/4 μ where ∆0 is proportional to the magnitude of the order parameter and nμ is the Landau level index at the Fermi