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Physical Society Colloquium
lattices of quantum systems interacting classically Eugene Tsiper Princeton University Due to narrow bandwidths, the electronic structure of organic molecular crystals is strikingly different from the conventional inorganic semiconductors, such as Si, in that the electronic polarization caused by charge carriers constitutes a major effect, with energy scale greater than transfer integrals or temperature. We present an approach to electronic polarization, in which individual molecules are dealt with rigorously as quantum-mechanical systems subject to classical external fields of all other molecules. Atom-atom polarizability tensor is introduced to describe self-consistent intramolecular charge redistribution. We calculate stabilization energies of the neutral lattice, of isolated charge carriers, and of electron-hole pairs. Dielectric tensors of two representative organic molecular crystals, computed to within experimental accuracy, suggest quantitative predictability of the new approach. Applying the method to crystalline thin films we find that electronic polarization is significantly different at a free surface, near a metal-organic interface, in thin organic layers, and in the bulk, leading to significant transport gap variations across organic films.
Tuesday, February 19th 2002, 16:00 |