Evidence for quantized displacement in nanomechanical oscillators.
Physicists at Boston University have performed an experiment in which
tiny silicon paddles, sprouting from a central stick of silicon like
the vanes from a heat sink, seem to oscillate together in a peculiar
manner: the paddles can travel out to certain displacements but not
to others. The setup for this experiment consists of a lithographically
prepared structure looking like a double-sided comb (see picture at
Next, a gold-film electrode
is deposited on top of the spine. Then a current is sent through
the film and an external magnetic field is applied. This sets the
structure to vibrating at frequencies as high as one gigahertz.
This makes the structure the fastest man-made oscillator. (Atoms
and molecules can vibrate faster than this, but not any chunk of
matter, until now.) At relatively warm temperatures, this rig,
small as it is, behaves according to the dictates of classical
physics. The larger the driving force (set up by the magnetic field
and the current moving through the gold electrode) the greater the
excursion of the paddles. This is no more than Hooke’s law.
At millikelvin temperatures, however, quantum mechanics takes over from
classical mechanics. In principle, the energies of the oscillating paddles
are quantized, and this in turn should show up as a propensity of the
paddles (500 nm long and 200 nm wide) to displace only by discrete amounts.
The Boston University experiment sees signs of exactly this sort of
et al., Physical Review Letters, 28 January 2005; contact Pritiraj
Mohanty, 617-353-9297, firstname.lastname@example.org; lab website, http://nano.bu.edu/quantum-motion.html