Infrared Cyclotron Resonance in Semiconducting Surface Inversion Layers

The frequency-dependent conductivity $\sigma \left(\omega \right)$ of a two-dimensional interacting electron gas in the presence of a random array of scattering centers and a dc magnetic field is studied. Electron-electron interaction effects enter $\sigma \left(\omega \right)$ through the holomorphic memory function $M\left(\omega \right)$ whose imaginary part is the inverse of the frequency-dependent relaxation time $\tau \left(\omega \right)$. A qualitative explanation of some of the perplexing results observed in infrared cyclotron resonance, including how electron-electron interactions affect both the fundamental and harmonics, is given.