Professor Garland is involved in the study of phase transitions and order-disorder phenomena, primarily in liquid crystal materials. Liquid crystals are especially interesting systems since they provide a rich variety of translational and orientational ordering. Emphasis is on rod-like molecules that exhibit several phases: nematic N (orientational order but no translational order of center-of-mass positions) and a variety of smectic Sm (layered structures with 1-D translational order). The goal is to understand the role of order-parameter symmetry, interaction range, and competing interactions in determining the stability of phases and the critical fluctuations near transitions between phases. High-resolution experimental techniques are required to characterize critical behavior and test statistical mechanical models. This group has developed computer-controlled ac calorimetric instruments well suited to the study of critical fluctuations in the energy near second-order transitions.

Recently this technique has been augmented by relaxation calorimetry (which allows the determination of small latent heats at weakly first order transitions) and dynamic calorimetry (where frequency-dependent Cp data provides a probe of the dynamics of cooperative phenomena). There are also opportunities to carry out high-resolution X-ray measurements.

In addition to the study of bulk materials near N-SmA, SmA-SmC, and several SmA-SmA' (A, A'= A1, A2, Ad) transitions, the phase behavior of liquid crystals in the fractal pores of very low density aerogels and in the presence of colloidal aerosil particles is also being investigated. In this case, random ordering fields due to interactions with the "walls" of the silica gels or sils greatly modify the behavior. The effect of quenched randomness on long-range order is a very challenging problem, previously studied primarily in mixed magnetic crystals. The ability to study several transitions in different universality classes for a single liquid crystal-aerogel/aerosil system and to tune the random field strength by varying gel porosity or sil concentration makes this new approach very promising.