Cyclotron resonance in the layered perovskite superconductor Sr₂RuO₄

We have observed cyclotron resonance in the layered perovskite superconductor Sr₂RuO₄. We obtain cyclotron masses for the α, β, and γ Fermi surfaces of (4.33±0.05)m_e, (5.81±0.05)m_e, and (9.71±0.2)m_e, respectively. The appreciable differences between these results and those obtained from de Haas–van Alphen measurements are attributable to strong electron-electron interactions in this system. Our findings appear to be consistent with predictions for an interacting Fermi liquid; indeed, semiquantitative agreement is obtained for the electron pockets β and γ.