Characteristic energy losses of electrons in a two-dimensional electron gas in a magnetic field

The electron energy loss function is calculated in the random phase approxi mation for a two-dimensional electron gas in a quantizing magnetic field. L ocal states of electrons at impurity atoms are taken into consideration. Th e energy losses due to one-particle and collective excitations of two-dimen sional electrons are determined. The activation of electrons localized at i mpurities leads to the emergence of steps on the dependence of loss functio n on the energy of an incident electron. Cerenkov losses associated with em ission of magnetoplasmons appear starting from a threshold velocity of the electron. When the velocity exceeds the threshold value significantly, the losses are due only to spontaneous emission of magnetoplasmons. The corresp onding loss function decreases in inverse proportion to the electron veloci ty. (C) 1999 American Institute of Physics. [S1063-777X(99)01012-9].