Probing many-body quantum states in single InAs quantum dots: Terahertz and tunneling spectroscopy

We have investigated the many-body quantum states in single InAs quantum dots (QDs) by simultaneously obtaining the terahertz (THz) intersublevel transition and single electron tunneling spectra. It is found that the intersublevel transition energies measured in the few-electron region are systematically larger than the excited state (ES) energies determined from the transport measurements. We show that tunneling and THz spectroscopy probe the same many-body excited states in the QDs, but their sensitivities depend on their selection rules. In the many-electron region, we observe THz peaks whose energies coincide with the tunneling ESs.