4. MAGNETIC-ELECTRIC AHARONOV-BOHM EFFECT IN METAL RINGS
In quantum mechanics, the Aharonov-Bohm effect occurs when a beam of
electrons, split into two beams that travel in opposite directions around a
region containing a magnetic flux, are then recombined with the result that
the intensity of the recombined electron beam oscillates periodically as the
enclosed magnetic field is varied. In general, a tunnel junction is a junction
(potential barrier) involving a thin separation between two conductors, with
the width of the junction equal to or less than the wavelength of the conduct-
ance entity (e.g., the wavelength of the electron). The essential result at a
tunnel junction is that the conductance entity can penetrate the barrier by
means of quantum mechanical "tunneling", this tunneling effect essentially
arising from the fact that with the wavelength of the particle larger than the
width of the barrier, the particle has a finite probability, as calculated
from its wave-equation, to be on both sides of the barrier at any instant. The
term "quantum interference" refers to an amplitude variation resulting from a
superposition (addition) of wave-functions. ... ... Van Oudenaarden et al
(4 authors at 2 installations, NL FR) report observations of the Aharonov-Bohm
effect in metal rings whose metallic continuity is broken by tunnel junctions,
and measurements of quantum interference of electrons in this system under the
influence of both magnetic and electrostatic potentials. The authors suggest
these two potentials play interchangeable roles in this system, and that this
type of experiment enables the direct measurement of the average diffusion
time of electrons in metals.
QY: Alexander van Oudenaarden <socrates@qt.tn.tudelft.nl>
(Nature 19 Feb 98)