TEMPERATURE-DEPENDENCE OF MAGNETORESISTANCE OSCILLATIONS IN A 2-DIMENSIONAL ELECTRON-GAS SUBJECTED TO A PERIODIC POTENTIAL

We have measured the magnetoresistance at various temperatures of a two-dimensional electron gas subjected to a one-dimensional periodic potential. A series of oscillations periodic in inverse magnetic field is observed at low fields due to a resonant drift of electrons in the periodic potential, while at higher fields the Shubnikov de Haas (SdH) oscillations are observed. The low-field oscillations persist to a much higher temperature than the SdH oscillations. We argue that the low-field oscillations are quenched when the thermal smearing of the cyclotron orbit diameter is equal to the period of the potential. Using this simple model, we show that the temperature at which the low-field oscillations are quenched is larger than that for the SdH oscillations by a factor kFa/2, where a is the period and kF the Fermi wave vector. In addition, an explicit expression for the temperature dependence of the low-field oscillations is calculated and compared with our experimental data. Excellent agreement is found between the predicted and observed temperature dependences. © 1990 The American Physical Society.