Far-infrared magneto-absorption of double-layer two-dimensional electron system in tilted magnetic fields

Far-infrared magneto-absorption of double-layer two-dimensional electron system has been measured by Fourier transform spectrometer in tilted magnetic fields. We have measured the dependence of cyclotron mass ( m C ) on the parallel ( B ∥ ) and perpendicular ( B ⊥ ) magnetic fields systematically. The obtained B ∥ dependence of m C is complicated and varies with B ⊥ , which cannot be explained by semi-classical theory.