SUPPRESSION OF THE ELECTRON-PHONON INTERACTION IN A QUANTIZING MAGNETIC-FIELD

The interaction of electrons with acoustic phonons in semiconductors i s governed by the strain-energy constants, which generally have differ ent magnitudes and different signs for electronic states in different bands. Accordingly, when states of different bands are mixed by extern al fields, the effective strain-energy constants, which are combinatio ns of the constants of the unperturbed bands, may vanish for certain e lectronic states. The effective strain-energy constants for a given st ate can be reduced to zero with the help of a set of controllable cont inuous parameters of the energy spectrum (the composition of the mater ial, the static strain, the magnetic field, etc.). The number of these parameters is no smaller than the number of constants which are to be made equal to zero. The mixing of states of GAMMA6 and GAMMA8 bands i n a direct-gap cubic semiconductor caused by a quantizing magnetic fie ld and a static deformation of the crystal has been studied. For a giv en magnetic field, expressions are derived for the static-stain tensor which corresponds to a suppression of the electron-phonon coupling in the ultraquantum limit. In this limit, the electron gas fills states only near the bottom of the lower Landau subband of the conduction ban d.