CONTINUED-FRACTION FORMALISM OF LINEAR DYNAMIC CONDUCTIVITY BY A COMBINED PROJECTION TECHNIQUE

Starting with the Liouville equation and with use of the combined projection technique presented earlier [J. Y. Sug, C. H. Choi, and S. D. Choi, Nuovo Cimento B 109, 177 (1994)], we obtain the ensemble average of current of many-electron systems in the presence of oscillatory electric fields. For quite weak fields the dynamic conductivity is given in a continued fraction form. The present form contains the first- and second-order correction parts, while the Mori type contains only the first-order part. © 1995 The American Physical Society.