Shell-tunneling Spectroscopy of the single-particle energy levels of insulating quantum dots

The energy levels of CdSe quantum dots are studied by scanning tunneling spectroscopy. By varying the tip-dot distance, we switch from "shell-filling" spectroscopy (where electrons accumulate in the dot and experience mutual repulsion) to "shell-tunneling" spectroscopy (where electrons tunnel, one at a time, through the dot). Shell-tunneling spectroscopy provides the single-particle energy levels of the CdSe quantum dot. The results of both types of tunneling spectroscopy are compared with pseudopotential many-body calculations.