Can ohmic spikes define quantum systems?

We investigate a system defined by an array of metallic spikes which extend down from an annealed Ni-AuGe metallisation deposited on the surface of an AlGaAs/GaAs heterostructure. For the case where the spikes penetrate the two dimensional gas (2DEG), we show that electrons injected from the spikes into the 2DEG maintain phase coherence at low temperatures, resulting in quantum interference processes determined by the spike distribution. A unique device which induces a topological transition from a Corbino disc to a Hall bar is employed to explore this novel phenomenon. We discuss refinements to the spiking process which will facilitate the incorporation of these metallic spikes into nanostructure designs.