Periodic conductance fluctuations and stable orbits in mesoscopic semiconductor billiards

We investigate electron interference in strongly confined GaAs/AlGaAs quantum dots, by studying the reproducible fluctuations in their low-temperature magneto-resistance. Spectral analysis of the fluctuations reveals a strong fundamental peak with well-defined harmonics, suggesting that transport can be dominated by the remnants of just a single classical orbit. The orbit is found to be relatively insensitive to changes in gate voltage or temperature, and its existence is also suggested by numerical simulations of the devices. Our results therefore demonstrate a survival of semi-classical ballistic transport that is very regular in mesoscopic devices, and so provide striking evidence that the remnants of certain classical orbits can be highly stable in the quantum environment.