Observation of quantum oscillations in Sr₂RuO₄

Sr 2RuO 4 was recently discovered to be the first layered perovskite superconductor (T c=1 K) containing no copper. Its normal state properties are also of interest, because it is strongly two-dimensional, like the high Tc cuprates, but differs from them in the type and concentration of carriers. It thus provides us with a new opportunity to shed light on the relative roles of reduced dimensionality versus other aspects of the electronic structure in producing anomalous normal state properties in layered metallic oxides. Here we report the observation of quantum oscillations in the resistivity and magnetisation of Sr 2RuO 4. Our findings are consistent with the existence of three partially filled energy bands giving almost cylindrical Fermi surfaces, the areas of which are in fairly good agreement with the predictions of electronic energy band structure calculations. However the cyclotron masses are considerably enhanced, showing the importance of correlations. In spite of the low dimensionality of Sr 2RuO 4, our observations are consistent with the predictions of the standard Fermi liquid theory of correlated electron systems