Fabry-Perot interferometry with electron waves

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Abstract
The authors have constructed a gated device on a high mobility GaAs-GaAlAs heterostructure which acts as a ballistic channel within a resonant cavity defined by reflectors at each end. Both the channel width and the separation of the reflectors are smaller than the electron mean free path, such that when the channel is defined, oscillations in the resistance are observed as the distance between the reflectors is reduced. When the width of the channel is wide in comparison with the width of the voltage, or current probes, non-local voltage fluctuations result in the measured resistance going to zero. At intermediate channel widths the resistance oscillations are periodic in the separation of the reflectors with a period equal to half the Fermi wavelength. In this regime gradually changing the width enables one to calculate the change in phase of the electron wavefunction as it passes through a one-dimensional subband, this being found to be in good agreement with experiment. When the channel is very narrow, the resistance shows peaks of up to 200% which arise because of the overall quantisation imposed by the cavity.