A direct calculation of the tunnelling current. II. Free electron description

Abstract

For Pt. I see ibid., vol.4., 916 (1971). The theory of tunnelling introduced in Pt. I is reformulated in the case of free electrons subjected to an arbitrary one-electron potential. An exact expression for the current is obtained, using Keldysh's generalization of perturbation theory. This result is particularly suited to an exact field theoretical treatment of many-body effects in the tunnelling junction.