We report cyclotron and magnetophonon resonance experiments on GaAs-GaAlAs heterojunctions as a function of temperature. The cyclotron mass shows an anomalous increase with temperature, which we attribute to strong screening of the electron-optic-phonon interaction at low temperatures suppressing the polaron mass enhancement. The magnetophonon resonance results yield phonon frequencies significantly below the bulk GaAs LO values, suggesting that the electrons are interacting with phonons associated with the interface.

• Received 18 August 1986

DOI:https://doi.org/10.1103/PhysRevLett.58.77