Abstract
A unified diagrammatic treatment of single and double electron photoemission currents is presented. The irreducible lesser density-density response function is the starting point of these derivations. Diagrams for higher order processes in which several electrons are observed in coincidence can likewise be obtained. For physically relevant situations, in which the photoemission cross-section can be written as the Fermi Golden rule, the diagrams from the nonequilibrium Green's function approach can be put in direct correspondence with the diagrams of the scattering theory.
Highlights
The electron photoemission is a process in which classical or quantized electromagnetic field interacts with a many-body target leaving the system in an unbound electronic state [1]
Progressing diagrammatically further [20] one realizes that dressing of this diagram leads to the renormalization of each electronic propagator involved, and generates vertex functions [21]. All these ingredients are important in different physical scenarios, they account for the effects of optical field screening [22,23,24], intrisic and extrinsic losses as well as their interference [25,26,27], and for the formation of the scattering states [28]
For completeness all leading order diagrams are shown on Fig. 3, where points labelled by α, β, γ denote integration over space, summation over spin, and integration over the time on “−”-branch of the Keldysh contour
Summary
The electron photoemission is a process in which classical or quantized electromagnetic field interacts with a many-body target leaving the system in an unbound electronic state [1]. First microscopic theories of photoemission [16, 17] have taken underlying electronic structure into account they have not provided a description of inelastic energy losses experienced by the liberated electron Such formulation was achieved with the help of non-equilibrium Green’s function approach by Caroli et al [18]. Progressing diagrammatically further [20] one realizes that dressing of this diagram leads to the renormalization of each electronic propagator involved, and generates vertex functions [21] All these ingredients are important in different physical scenarios, they account for the effects of optical field screening [22,23,24], intrisic and extrinsic losses as well as their interference [25,26,27], and for the formation of the scattering states [28].
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