OPTICAL CONDUCTIVITY OF THE BECHGAARD SALTS - THE SUM-RULES REVISITED

The validity of the optical sum rules has been addressed eversince and was always matter of debate. Particularly controversial is the proof that the partial sum rules can be extended to both optical conductivit y and energy loss function. We show in this paper that for both transv erse (optical conductivity) and longitudinal (energy loss function) ab sorption processes the corresponding sum rule can be theoretically est ablished and through appropriate conditions for the integration limits exactly verified. We also focus our attention on the one-dimensional case within the microscopic Hubbard model. An application of these con cepts to the quasi one-dimensional systems, for which we have chosen t he organic (TMTSF)(2)PF6 material, will also be presented.