Imaging coherent electron wave flow in a two-dimensional electron gas

We present images of coherent electron wave flow from a quantum point contact (QPC) formed in a two-dimensional electron gas (2DEG). Near the QPC these images closely resemble the expected wavefunctions for electrons passing through the lowest transverse modes of the QPC. Farther away from the QPC the flow through the 2DEG bulk shows strong branching behavior. The branching behavior is due to the cumulative effect of electrons passing over many small bumps and dips in the potential that they feel in the 2DEG. All of the images are decorated with fringes spaced by half the Fermi wavelength that persist out to the edges of the areas scanned. Images showing the effect of moving the position of the QPC are also presented.