Authors: J.K. Freericks, T.P. Devereaux, and R. Bulla
Journal:
Acta Physica Polonica B 32, 3219 (2001)
A wide variety of strongly correlated insulators ranging from intermediate valence materials, to Kondo insulators, to underdoped high-temperature superconductors display anomalous behavior in their inelastic light scattering. The Raman response in these materials show a low-temperature transfer of spectral weight from low to high energy (as T is reduced), the appearance of an isosbestic point (a characteristic frequency where the Raman response is independent of temperature), and a large ratio of twice the ``spectral gap'' to the ``onset temperature'' where the low-energy spectral weight begins to deplete. We illustrate how these features generically appear in the Raman response of model systems that are tuned to lie just on the insulating side of the metal-insulator transition. We solve for the Raman response in the Falicov-Kimball model and in the Hubbard model. In the latter case, we find a number of new features arise as one approaches the metal-insulator transition from the metallic Fermi-liquid phase. Such behavior has not yet been seen in experiment.