Magneto-optical measurements of β-(BEDT-TTF)2AuI2

Magneto-optical measurements of β-(BEDT-TTF) 2 AuI 2 , which has an isotropic two dimensional Fermi surface in the ab-plane, have been performed at 1.8 K by using cavity perturbation technique with steady magnetic field and mosaic transmission technique with pulsed magnetic field. A cyclotron resonance coming from the quasi two dimensional Fermi surface has been observed in both measurements for H⊥ab-plane. Obtained effective mass was 0.9 m c and this result is smaller than the mass obtained by the Shubnikov-de Haas measurement, which suggests the existence of electron-electron interactions in the system.