QUANTUM OSCILLATION IN THE SUPERCONDUCTING VORTEX STATE OF CERU2

We have succeeded in growing high-quality single crystals of CeRu2 and have observed dHvA oscillations both in the normal and superconductin g vortex (mixed) states. The detected dHvA frequencies have been well explained by the result of band-structure calculations. The dHvA frequ ency does not change in magnitude between the normal and superconducti ng states, while the cyclotron mass is reduced and the Dingle temperat ure is enhanced in the vortex state. The mass and the Dingle temperatu re depend on the magnetic field in the vortex state. (C) 1998 Elsevier Science B.V. All rights reserved.