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Negative PoissonÕs ratios are predicted for body-centered-cubic phases that
likely exist in white dwarf cores and neutron star outer crusts, as well as those
found for vacuumlike ion crystals, plasma dust crystals, and colloidal crystals
(including certain virus crystals). The existence of this counterintuitive property,
which means that a material laterally expands when stretched, is experimentally
demonstrated for very low density crystals of trapped ions. At very
high densities, the large predicted negative and positive PoissonÕs ratios might
be important for understanding the asteroseismology of neutron stars and
white dwarfs and the effect of stellar stresses on nuclear reaction rates. Giant
PoissonÕs ratios are both predicted and observed for highly strained coulombic
photonic crystals, suggesting possible applications of large, tunable PoissonÕs
ratios for photonic crystal devices.
Rubber bands, Jell-O, and soft biological tissues
share an important and unusual property
with ultradense crystals in neutron stars and
white dwarfs (1–3), vacuumlike ion crystals in
electromagnetic traps (4–6), and crystallized
colloids (7–16). ...
The experimentally determined
results (F) are for a four-layer stack
of 9Be1 ions in a Penning trap, which is highly
extended in two in-plane directions, [11#0] and
. The solid curves are theoretical predictions
for a four-layer ion crystal and for a
three-dimensionally inÞnite ion crystal