Polarons in electron-populated quantum dots revealed by resonant Raman scattering

Abstract

We report on the direct observation of polarons in $\mathrm{In}\mathrm{As}∕\mathrm{Ga}\mathrm{As}$ self-assembled quantum dots (QD) populated by few electrons. The polarons are strongly coupled modes of QD phonons and electron intersublevel transitions. The degree of coupling is varied in a systematic way with a set of samples having electron intersublevel spacing changing from larger to smaller than the longitudinal-optical-phonon energy. The signature of polarons is evidenced clearly by the observation of a large $(12--20\phantom{\rule{0.3em}{0ex}}\mathrm{meV})$ anticrossing for both InAs and GaAs-like QD phonons using resonant Raman spectroscopy.