Quantum Dots and Artificial Atoms

Abstract

When a small dot is weakly coupled to reservoirs via small tunnel junctions, addition of an extra electron into the dot raises the electrochemical potential of the dot. The one-by-one change of the number of electrons N in the dot leads to a conductance oscillation as a function of a gate voltage (called the Coulomb oscillation or Coulomb blockade oscillation). The oscillation period is usually constant for a system containing many electrons. However, in a small dot containing just a few electrons, both electron-electron interactions and quantum confinement effects become sufficiently strong to cause a significant modification of the Coulomb oscillation [1–3]. Such a system can be regarded as an artificial atom [4]. There have been several experiments on quantum dots containing only a few electrons. These include transport through a two-terminal asymmetric double-barrier tunneling structure [5–8] and through a gated double-barrier tunneling structure [2,3,9–11], and capacitance measurements of a vertically gated modulation-doped heterostructure [1,12]. In this section we describe transport measurements on a sub-micron gated double-barrier structure.