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A NUMBER OF biological processes such as the contraction of muscles
and the transport of ions and molecules within cells, are based on a
fascinating physical principle: In periodic, asymmetric potentials, the
random motion of Brownian particles can be rectified to do useful work. Devices
in which this effect occurs called ratchets
only apparently violate the second law of thermodynamics: energy
from external fluctuations is always dissipated during ratchet operation,
in agreement with the second law.
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We use semiconductor nanostructures to create ratchets for electrons. This
allows us to study 'quantum ratchets' rectifiers that are based on quantum effects
like
electron wave interference and tunnelling (Physics
World, March 1999, p.21).
Heiner Linke,
Richard Newbury
& Richard Taylor |
