Single-Dot Spectroscopy via Elastic Single-Electron Tunneling through a Pair of Coupled Quantum Dots

We study the electronic structure of a single self-assembled InAs quantum dot by probing elastic single-electron tunneling through a single pair of weakly coupled dots. In the region below pinch-off voltage, the nonlinear threshold voltage behavior provides electronic addition energies exactly as the linear, Coulomb blockade oscillation does. By analyzing it, we identify the $s$ and the $p$ shell addition spectrum for up to six electrons in the single InAs dot, i.e., one of the coupled dots. The evolution of the shell addition spectrum with magnetic field provides Fock-Darwin spectra of the $s$ and $p$ shells.