Single-electron tunneling through a double quantum dot: The artificial molecule

Single-electron tunneling through two coupled quantum dots is strongly influenced by the electrostatic interaction between the dots. At low temperatures, we observe the formation of a molecularlike state in the double-dot system. The dots are defined by split gates in an ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As-GaAs heterostructure. They are of different size and coupled in series, leading to two different charging energies. In the linear transport regime we find the charging diagram for the double quantum dot. This diagram exhibits the operation points of the system to be employed as an electron pump. © 1996 The American Physical Society.