Condensed Matter / Liquid Crystals
Professor Paul Keyes
When dealing with large organic molecules one frequently finds that there are several stable phases between the solid and liquid. Our research uses a combined theoretical and experimental approach towards the elucidation of the structures of these liquid crystalline "mesophases" and their physical properties. We are particularly interested in investigating the critical phenomena associated with the phase transitions between these various phases. One main focus of our work is on the role that chirality (optical activity) plays in producing structures and phase transitions. Experimentally we use various optical probes such as polarization microscopy, interferometry, and laser light scattering, including photon correlation spectroscopy. Theoretically we work with the phenomenological Landau theory of phase transitions. In recent years we have studied: (1) chiral smectic phases, which display ferroelectric and antiferroelectric behavior; (2) lyotropic nematic phases formed by mixtures of water with detergents; (3) organometallic mesogens, a new class of liquid crystals having both magnetic and conducting properties; and (4) cholesteric blue phases, some of the most exotic structures found in condensed matter physics, whose complexity derives entirely from their strong chirality.