Coulomb charging effects in an open quantum dot device

In this work we clarify the nature of frequent oscillations of the conductance of open quantum dots that were reported by Liang et al (Liang C-T et al 1998 Phys. Rev. Lett. 81 3507). Continuous and almost periodic oscillations superimposed upon ballistic conductance features are observed when the conductance G of the dot changes within a wide range 0< G <6 e 2 / h . We confirm the single-electron origin of the conductance oscillations by means of measurements in a perpendicular magnetic field and calculation of capacitances of the quantum dot with respect to two-dimensional (2D) electron gas reservoirs and gates. The calculations of the three-dimensional electrostatics of the device and 2D transport through the dot show that the progression of the Coulomb oscillations into the region G >2 e 2 / h is the consequence of suppression of inter-one-dimensional-subband scattering. The theory of Coulomb blockade and the Landauer formula are modified for the case of the quasi-one-dimensional system to describe combined charging and ballistic transport through the dot. Measured dependences of the conductance on the gate voltages and its temperature behaviour are correctly reproduced by the calculations.