Imaging Coherent Electron Flow from a Quantum Point Contact
M. A. Topinka,1
B. J. LeRoy,1
S. E. J. Shaw,1
E. J. Heller,1
R. M. Westervelt,1*
K. D. Maranowski,2
A. C. Gossard2
Scanning a charged tip above the two-dimensional
electron gas inside a gallium arsenide/aluminum gallium arsenide
nanostructure allows the coherent electron flow from the lowest
quantized modes of a quantum point contact at liquid helium
temperatures to be imaged. As the width of the quantum point contact is
increased, its electrical conductance increases in quantized steps of 2 e2/h, where e is the
electron charge and h is Planck's constant. The angular
dependence of the electron flow on each step agrees with theory, and
fringes separated by half the electron wavelength are observed. Placing
the tip so that it interrupts the flow from particular modes of the
quantum point contact causes a reduction in the conductance of those
particular conduction channels below 2 e2/h without affecting other
channels.
1 Division of Engineering and Applied Sciences,
Department of Physics, and Department of Chemistry and Chemical
Biology, Harvard University, Cambridge, MA 02138, USA.
2 Materials Department, University of California,
Santa Barbara, CA 93106, USA.
*
To whom correspondence should be addressed. E-mail:
westervelt{at}deas.harvard.edu
