Negative Poisson's ratios for extreme states of matter

Negative Poisson's ratios are predicted for body-centered-cubic phases that Likely exist in white dwarf cores and neutron star outer crusts, as well a s those found for vacuumlike ion crystals, plasma dust crystals, and colloi dal crystals (including certain virus crystals). The existence of this coun terintuitive property, which means that a material laterally expands when s tretched, is experimentally demonstrated for very low density crystals of t rapped ions. At very high densities, the large predicted negative and posit ive Poisson's ratios might be important for understanding the asteroseismol ogy of neutron stars and white dwarfs and the effect of stellar stresses on nuclear reaction rates. Giant Poisson's ratios are both predicted and obse rved for highly strained coulombic photonic crystals, suggesting possible a pplications of large, tunable Poisson's ratios for photonic crystal devices .