Fermi Surface Properties in Sr_<b>2</b>RuO_<b>4</b>

Abstract

We measured the de Haas-van Alphen (dHvA) effect, magnetoresistance and specific heat to clarify the two-dimensional Fermi surface properties of Sr 2 RuO 4 . From the angular dependence of the dHvA amplitude, we determined the Yamaji angle for three quasi-cylindrical Fermi surfaces α, β and γ to be 30.6° for the Fermi surface α, about 30° for β and 15.3° for γ. The cyclotron masses of sum and difference oscillatory components, m * β±α and m * γ±α , are found to be highly different from m * β + m * α and m * γ + m * α , respectively, for any field direction. The dHvA oscillation due to sums and differences is not due to the magnetic interaction but to the chemical potential oscillation for quasi-two-dimensional Fermi surfaces. The specific heat data are discussed from a viewpoint of a characteristic energy gap in a possible p -wave superconductor Sr 2 RuO 4 .