Destruction of magnetophonon resonance in high magnetic
fields from impurity and phonon scattering in heterojunctions
1Xu Wen, 2F.M. Peeters,
2J.T. Devreese, 3D.R. Leadley
and 3R.J. Nicholas
- Dept. of Theoretical Physics, Australian National University, Canberra,
ACT 0200, Australia
- Dept. Natuurkunde, Universiteit Antwerpen (UIA), Universiteitsplein
1, B-2610 Antwerpen, Belgium
- Dept of Physics, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU,
UK.
We present a detailed theoretical calculation to explain the collapse
of the magnetophonon resonance (MPR) effect in high magnetic fields in
certain high mobility AlGaAs/GaAs heterojunction samples. The magnetoresistivity
(
)
and the density of states (DOS) are calculated self-consistently. We include
the interaction of electrons with background and remote impurities, with
acoustic-phonons via deformation potential 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 ;
and iii) strong impurity scattering leads to a shift of the DOS
peaks to lower energy. An increase in LL width will reduce the additional
resonant LO-phonon scattering, but also decrease the contribution to
from all scattering mechanisms due to the reduction in DOS.
Near the MPR condition there are thus two competing processes:
increases due to LO-phonon scattering; but this increases the LL width
and so reduces the contribution to
from elastic scattering. In certain samples we found that the two effects
balanced at high magnetic fields resulting in the disappearance of MPR
oscillations from .
International Journal of Modern Physics B, 10, 169-202 (1996)