de Haas-van Alphen effect of the heavy-fermion superconductor URu_2Si_2

摘要

We have measured the de Haas-van Alphen (dHvA) effect of URu_2Si_2. One kind of the dHvA branch, which corresponds to an almost spherical Fermi surface, has been detected both in the normal and super-conducting mixed states. The dHvA frequency in the mixed state is unchanged from the normal state. The cyclotron effective mass is clearly found to decrease with decreasing the magnetic field below H_(c2) and the corresponding Dingle temperature increases with decreasing the field.