We have observed a terahertz (THz) induced single electron photovoltaic effect in self-assembled InAs quantum dots (QDs). We used a single electron transistor (SET) geometry that consists of a single InAs QD and nanogap electrodes coupled with a bowtie antenna. Under a weak, broadband THz radiation, a photocurrent induced by THz intersublevel transitions in the QD is generated even when no bias voltage is applied to the SET. The observed single electron photovoltaic effect is due to an energy-dependent tunneling asymmetry in the QD-SET. Moreover, the tunneling asymmetry changes not only with the shell, but also with the electron number in the QD, suggesting the manybody nature of the electron wavefunctions. The THz photovoltaic effect observed in the present QD-SET system may have potential applications to nanoscale energy harvesting.
