Roto-electrics: Arrays of interacting polar molecular rotors

ORGN 13

John C. Price, Robert Horansky, Erick Winston, Jason Underwood, and Matthew Myers. Department of Physics, University of Colorado, 390 UCB, Boulder, CO 80309
Synthesized dipolar molecular rotors offer a new bottom-up approach to polar molecular electronic materials. Arrays of polar rotors are expected to have ferroelectric or antiferroelectric ground states, with polar rotary phonons propagating at velocities that may be lower than those of sound waves in conventional polar condensed media. Ferroelectric molecular rotor crystals could have several interesting applications, including compact rf filters and fast electro-optic switches. We will present dielectic spectroscopy results on several crystalline rotor systems, including a three-dimensional collection of fluorobenzene rotors and a cryptophane system. In the fluorbenzene system the rotational motion proceeds by thermal hopping in a rotational potential with two minima, and both the barrier height and the asymmetry of the potential can be measured by dielectric spectroscopy. An analysis of the temperature dependence of the dielectric loss peaks yields evidence for rotor-rotor interactions and polar ordering.