DE HAAS-VAN-ALPHEN OSCILLATIONS IN A SUPERCONDUCTING STATE AT HIGH MAGNETIC-FIELDS

Low-temperature quantum oscillations of the de Haas van Alphen (dHvA) amplitude are shown to persist far below the upper critical field of a strongly type-II superconductor, due to the gapless nature of the BCS quasiparticle spectrum in high fields. The dHvA amplitude in the superconducting state is smaller than its normal state counterpart by the factor [max(T,)/]2, where is the damping. This factor reflects the presence of a small gapless portion of the Fermi surface, surrounded by regions where the BCS gap is large. The agreement with recent experimental data on V3Si is very good. © 1995 The American Physical Society.