Coulomb Charging Effects in an Open Quantum Dot Device at Zero Magnetic Field

We report low-temperature conductance measurements of an open quantum dot device formed in a clean one-dimensional (1D) channel. At zero magnetic field, continuous and periodic oscillations superimposed upon 1D ballistic conductance steps are observed. We ascribe the observed conductance oscillations when the conductance through the dot G exceeds 2e2/h, to experimental evidence for Coulomb charging effects in an open dot. This is supported by the evolution of the oscillating features for G>2e2/h as a function of both temperature and barrier transparency.