Effects of electron-phonon interactions on the electron tunneling spectrum of PbS quantum dots
Résumé
We present a tunnel spectroscopy study of single PbS quantum dots (QDs) as a function of temperature and gate voltage. Three distinct signatures of strong electron-phonon coupling are observed in the electron tunneling spectrum (ETS) of these QDs. In the shell-filling regime, the 8× degeneracy of the electronic levels is lifted by the Coulomb interactions and allows the observation of phonon subbands that result from the emission of optical phonons. At low bias, a gap is observed in the ETS that cannot be closed with the gate voltage, which is a distinguishing feature of the Franck-Condon blockade. From the data, a Huang-Rhys factor in the range S ∼ 1.7–2.5 is obtained. Finally, in the shell-tunneling regime, the optical phonons appear in the inelastic ETS d 2 I/dV 2 .
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