Electron - phonon interaction in semiconductor heterostructures
École Normale Supérieure, Paris, France
Thursday, December 3, 2009, 2:00 PM
Seminar Room F
We shall present theoretical and experimental results that show that the
very same interaction, namely the Fröhlich coupling between electrons and
optical phonons, lead to a weak coupling in 3D/2D electron states while
electrons in III-V or II-VI Quantum Dots enter a strong coupling with the
LO phonons and form polarons.
A particular attention has been paid to measure and interpret the energy
relaxation in QD's where the S-P transition energy is far below the LO
phonons. Pump and probe experiments and modeling of the energy relaxation
from the upper states point out that the dominant mechanism is the
coupling of the polarons to the 2 phonons reservoir due to anharmonicity
down to THz energies.
The situation of QW's in a strong magnetic field is more involved since
the electron - phonon interaction is neither weak nor are the magneto -
polarons long lived enough to support the strong coupling description.
This work has been done in collaboration with the Sheffield group and the
Dresden free electron laser group.