Direct observation of magnetophonon resonances in Landau-level lifetimes of a semiconductor heterostructure

Landau-level lifetimes are determined from saturation cyclotron resonance measurements on an InAs/GaSb double heterojunction using a picosecond far-infrared free-electron laser. Strong nonparabolicity of the conduction band truncates the equidistant Landau-level ladder, and saturation is achieved at all wavelengths. The Landau-level lifetimes show minima at NHBAR omega(c) = HBAR omega(LO), a direct observation of the magnetophonon effect. Observed picosecond lifetimes are due to LO-phonon emission which dominates electron-electron scattering at the magnetophonon resonance condition.