Fermi surface properties of YbCu2Si2

We succeeded in growing high-quality single crystals of a heavy electron compound YbCu 2 Si 2 . The electronic specific heat coefficient γ is determined to be 150 mJ/K 2 ·mol, which is consistent with the A value of the electrical resistivity from Kadowaki-Woods relation. We succeeded in observing the de Haas-van Alphen (dHvA) oscillations. The dHvA frequencies and large cyclotron effective masses in YbCu 2 Si 2 are highly different from those in a non-4f reference compound YCu 2 Si 2 . From these dHvA results, the heavy electron state of YbCu 2 Si 2 is characterized by the large contribution of 4f-electrons to the topology of the Fermi surface and also to the strong enhancement of effective mass caused by the spin fluctuations.