2-BAND DENSITY-MATRIX THEORY - THE EFFECT OF EXTERNAL FIELDS ON TRANSITION AND TRANSPORT PROCESSES

We present a derivation of the two-band density matrix dynamics which considers the effect of external fields on both the intraband drift motion in the six-dimensional configuration space and the interband transitions. This includes in particular the contribution of the light field to the drift term of the interband density matrix which is, for example, responsible for the 'resonant' Stark effect. A relation between the density matrix and electrodynamic quantities is established where our approach directly accounts for the decomposition into interband and intraband polarization. The consideration of a static magnetic field without invoking the 'Peierls substitution' turns out to yield deviations from the usual formulations in magneto-optics and transport theory. In the regime of quantum transport we obtain a general expression for the quantum correction of the energy density which is valid for non-equilibrium conditions and arbitrary band structure and can be used for the deviation of quantum hydrodynamic equations.