Physics Colloquium, 24 April, 2001

Imaging Coherent Electron Flow

R.M. Westervelt

Harvard University

Scanning a charged tip above the two dimensional electron gas inside a GaAs/AlGaAs heterostructure images coherent electron flow from a quantum point contact at liquid He temperatures. As the width of the quantum point contact (QPC) is increased, its electrical conductance increases in quantized steps of 2e^2/h. The angular dependence of the electron flow on each step agrees with theory, forming broad lobes at submicron distances from the QPC, and fringes separated by half the electron wavelength are observed. At distances above 1 micron, the electron flow forms narrow channels as a consequence of small angle scattering, in agreement with recent theory for a QPC in a high mobility two dimensional electron gas.

3.30 p.m., Smith Laboratory, Room 1005

Refreshments served in Smith 1094 at 3:00 p.m.