Photon drag in single and multiple two-level quantum wells

Starting from a density-matrix operator description we derive an expression for the photon-drag response tensor of a quantum-well system containing an arbitrary number of subbands. Subsequently we analyze the structure of the nonlinear response tensor and make a specialization to the case of a two-level quantum well. In the wake of a self-consistent calculation of the local fields in a two-level well and in multiple quantum wells the photon-drag currents are determined. We illustrate the main ingredients of our theory by carrying out a number of numerical calculations of the drag current in a 15-Angstrom wide niobium quantum well deposited on a crystalline quartz substrate and a GaAs/AlxGa1-xAs multiple-quantum-well structure. In particular we pay attention to the frequency, angle of incidence, and number of wells dependencies of the current, and we demonstrate that local-field effects may give rise to a significant blueshift and an asymmetric form of the resonance peak.