Plasmon-phonon coupling in charged n-type CdSe quantum dots: A THz time-domain spectroscopic study

This work aims to experimentally determine the polarizability of confined electron in CdSe quantum dots (QD). The dielectric response of uncharged and charged CdSe quantum dots (3.2 and 6.3 nm) has been measured using terahertz time-domain spectroscopy in the frequency range of 2.0-7.0 THz. A strong coupling between the surface plasmon and surface phonons appears upon charging the QDs. The absolute polarizability of an electron in 3.2 and 6.3 nm charged QDs are experimentally determined to be 0.5 +/- 0.1 x 10(3) angstrom(3) and 14.6 +/- 0.3 x 10(3) angstrom(3), respectively, and the values agree reasonably well with theory and the previous experiment. The observed plasmon-phonon coupling is expected to play an important role in electron relaxation in absence of a hole in CdSe QDs.