W. Xu et al., DESTRUCTION OF MAGNETOPHONON RESONANCE IN HIGH MAGNETIC-FIELDS FROM IMPURITY AND PHONON-SCATTERING IN HETEROJUNCTIONS, International journal of modern physics b, 10(2), 1996, pp. 169-202
We present a detailed theoretical calculation to explain the collapse
of the magnetophonon resonance (MPR) effect in high magnetic fields in
certain high mobility Al-GaAs/GaAs heterojunction samples. The magnet
oresistivity (rho(xx)) and the density of states (DOS) are calculated
self-consistently. We include the interaction of electrons with backgr
ound and remote impurities, with acoustic-phonons via deformation pote
ntial and piezoelectric coupling, and with optic (LO) phonons. We find
that: (i) the DOS is modified strongly by both elastic and inelastic
scattering; (ii) the Landau-level (LL) width oscillates with magnetic
fields commensurate with the MPR oscillations in rho(xx); and (iii) st
rong impurity scattering leads to a shift of the DOS peaks to lower en
ergy. An increase in LL width will reduce the additional resonant LO-p
honon scattering, but also decrease the contribution to rho(xx) from a
ll scattering mechanisms due to the reduction in DOS. Near the MPR con
dition there are thus two competing processes: rho(xx) increases due t
o LO-phonon scattering; but this increases the LL width and so reduces
the contribution to rho(xx) from elastic scattering. In certain sampl
es we found that the two effects balanced at high magnetic fields resu
lting in the disappearance of MPR oscillations from rho(xx).