Aharonov-Bohm (AB) oscillations are studied for a parallel-coupled vertical double quantum dot with a common source and drain electrode. We observe AB oscillations of current via a one-electron bonding state as the ground state and an antibonding state as the excited state. As the center gate voltage becomes more negative, the oscillation period is clearly halved for both the bonding and antibonding states, and the phase changes by half a period for the antibonding state. This result can be explained by a calculation that takes account of the indirect interdot coupling via the two electrodes.

We investigate three vertical quantum dots (QDs) laterally coupled in a triangular arrangement forming a triple QD (tQD) with common source and drain electrodes. The three equidistant dot mesas each have one gate electrode allowing control of the electrochemical potential in each QD. From the stability diagrams observed by measuring current through the tQD on sweeping the voltages on two of the gate electrodes for different values of voltage on the third gate electrode, we build up part of the three-dimensional stability diagram. Our device can be useful to reveal the consequences of interdot coupling on electronic states in tQDs.

Resonance-hybrid states in a triple quantum dot Amaha, S.; Hatano, T.; Tamura, H.; Teraoka, S.; Kubo, T.; Tokura, Y.; Austing, D. G.; Tarucha, S.

We demonstrate one and two photoelectron trapping and the subsequent dynamics associated with interdot transfer in double quantum dots over a time scale much shorter than the typical spin lifetime. Identification of photoelectron trapping is achieved via resonant interdot tunneling of the photoelectrons in the excited states. The interdot transfer enables detection of single photoelectrons in a nondestructive manner. When two photoelectrons are trapped at almost the same time we observed that the interdot resonant tunneling is strongly affected by the Coulomb interaction between the electrons. Finally the influence of the two-electron singlet-triplet state hybridization has been detected using the interdot tunneling of a photoelectron.