Optical Spectroscopic Observation of Quantum Oscillations of the 2D Fermi Energy with Magnetic Field

Absorption and reflection spectroscopy of the 2D electron gas in GaAs quantum wells exhibits sharp features due to transitions between electron and hole Landau levels. For increasing magnetic field, we observe new absorption peaks at integer filling factors, corresponding to abrupt changes in the Fermi energy. As the Fermi energy moves into a lower Landau level, new states at lower energy become available for absorption. Fermi energy oscillations are observed at the filling factors of 2, 4, 6, and 8 - i independent of carrier density for three different samples. Simultaneous emission spectroscopy exhibits the previously observed characteristic plateaus and large variations in intensity with magnetic field.