Spin channel Keldysh field theory for weakly interacting quantum dots

TL;DR

This paper introduces a low-energy nonequilibrium field theory for weakly interacting quantum dots using the Keldysh formalism, effectively capturing conductance behavior at low temperatures and weak interactions.

Contribution

It develops a simplified Keldysh field integral approach in the spin channel, accurately describing nonequilibrium quantum dots and their conductance in the weak interaction regime.

Findings

Correctly describes the conductance maximum in the unitary limit

Applicable to low-temperature, weakly interacting quantum dots

Provides an alternative method for studying nonequilibrium nanodevices

Abstract

We develop a low-energy nonequilibrium field theory for weakly interacting quantum dots. The theory is based on the Keldysh field integral in the spin channel of the quantum dot described by the single impurity Anderson Hamiltonian. The effective Keldysh action is a functional of the Hubbard-Stratonovich magnetization field decoupling the quantum dot spin channel. We expand this action up to the second order with respect to the magnetization field, which allows to describe nonequilibrium interacting quantum dots at low temperatures and weak electron-electron interactions,up to the contacts-dot coupling energy. Besides its simplicity, an additional advantage of the theory is that it correctly describes the unitary limit giving the correct result for the conductance maximum. Thus our theory establishes an alternative simple method relevant for investigation of weakly interacting nonequilibrium nanodevices.