Periodic magnetoconductance fluctuations in triangular quantum dots in the absence of selective probing

We have studied the magnetoconductance of quantum dots with triangular symmetry and areas down to 0.2 mu m(2), made in a high mobility two-dimensional electron gas embedded in a GaAs-AlxGa1-xAs heterostructure. Semiclassical simulations show that the gross features in the measured magnetoconductance are caused by ballistic effects. Below 1 K we observe a strong periodic oscillation, which may be explained in terms of the Aharanov-Bohm flux quantization through the area of a single classical periodic orbit. From a numerical and analytical analysis of possible trajectories in hard-and soft-walled potentials, we identify this periodic orbit as the enscribed triangle. Contrary to other recent experiments, this orbit is not accessible by classical processes for the incoming collimated beam.