AC linear response of a resonant tunneling system

The Keldysh-Green function technique in the representation of scattering st ates is applied to study the alternating current (AC) Linear current respon se of a mesoscopic tunneling junction. It is shown that, despite the genera lly accepted viewpoint [M. Buttiker, Phys. Rev., B45, 3807 (1992)], in the one-electron approximation the linear AC current response of the system can not be expressed in terms of the one-electron scattering matrix. However, t he response is completely determined by the full set of true electron wave functions in the region of the potential barrier. Our approach is used to c onsider the behavior of a resonant tunneling system under the influence of a weak coherent radiation field. In addition to high-frequency device appli cations, the study of the dynamical conductance has fundamental importance in that it provides information about the structure of the potential barrie r. (C) 2000 John Wiley & Sons, Inc.