Kondo effect in interacting nanoscopic systems: Keldysh field integral theory

TL;DR

This paper develops a transparent analytical Keldysh field theory to accurately describe the Kondo effect in strongly interacting nanoscale systems at temperatures near or above the Kondo temperature, applicable to complex many-body spectra.

Contribution

It introduces a universal nonequilibrium Keldysh field theory for strongly interacting systems, incorporating multiple slave-boson degrees of freedom for accurate modeling.

Findings

Validates the theory near the Kondo temperature.

Applicable to systems with complex many-body spectra.

Describes weak slave-bosonic oscillations induced by tunneling.

Abstract

Kondo physics in nonequilibrium interacting nanoscale devices is an attractive fundamental many-particle phenomenon with a rich potential for applications. Due to enormous complexity its clear and flexible theory is still highly desirable. We develop a physically transparent analytical theory capable to correctly describe the Kondo effect in strongly interacting systems at temperatures close to and above the Kondo temperature. We derive a nonequilibrium Keldysh field theory valid for a system with any finite electron-electron interaction which is much stronger than the coupling of the system to contacts. Finite electron-electron interactions are treated involving as many slave-boson degrees of freedom as one needs for a concrete many-body system. In a small vicinity of the zero slave-bosonic field configuration weak slave-bosonic oscillations, induced by the dot-contacts tunneling, are described by an effective Keldysh action quadratic in the slave-bosonic fields. For clarity the theory is presented for the single impurity Anderson model but the construction of the Keldysh field integral is universal and applicable to systems with more complex many-body spectra.