The electron transport through a quantum dot in the Coulomb blockade regime: Non-equilibrium Green's functions based model

TL;DR

This paper models electron transport through a quantum dot transitioning from Coulomb blockade to Kondo regime using nonequilibrium Green's functions, revealing characteristic features in the current-voltage behavior.

Contribution

It introduces a NEGF-based model that captures the transition from Coulomb blockade to Kondo regime in quantum dots with detailed I-V characteristics.

Findings

I-V characteristics show two steps in Coulomb blockade regime

Step locations depend on energy level and Coulomb interaction

Step height ratio is 2:1, consistent with transition rate results

Abstract

We explore electron transport through a quantum dot coupled to the source and drain charge reservoirs We trace the transition from the Coulomb blockade regime to Kondo regime in the electron transport through the dot occuring when we gradually strengthen the coupling of the dot to the charge reservoirs. The current-voltage $(I-V)$ characteristics are calculated using the equations of motion approach within the nonequilibrium Green's functions formalism (NEGF) beyond the Hartree-Fock approximation. We show that within the Coulomb blockade regime the $I-V$ characteristics for the quantum dot containing a single spin-degenerated level with the energy $E_0 $ include two steps whose locations are determined by the values of $ E_0 $ and the energy of Coulomb interaction of electrons in the dot $U.$ The heights of the steps are related as $2:1$ which is consistent with the results obtained by means of the transition rate equations.