Light Scattering Studies of the Two-Dimensional Phase Transition in Squaric Acid

Abstract

Crystalline squaric acid, H₂C₄O₄, has attracted considerable interest among physicists due to its simple planar geometry [1] and the existence of a structural phase transition at about 100 C [2]. Since proton ordering in hydrogen “bonds seems to play a key role in the phase change, it was soon realized that one had at hand a material which might show interesting two-dimensional Ising-type behaviour [3]. Information gained from birefringence studies [2] and neutron scattering [3] did in fact support such a view.