On the basis of Tani’s formalism for nonlinear response, a closed-form expression of the field-dependent dc conductivity is introduced. The field-dependent dc conductivity of electron-background (impurity and phonon) systems is evaluated by using the Mori-type projection technique. We also obtain the field-dependent self-energy operators, which show that the collisional broadening appears in both weak and high fields, while the intracollisional field effect is observed only in high field, as predicted by Barker. The results are compared with the work of some other authors.

• Received 25 July 1991

DOI:https://doi.org/10.1103/PhysRevB.44.11328