Coulomb interaction and transient charging of excited states in open nanosystems

TL;DR

This paper investigates how electron-electron Coulomb interactions influence time-dependent current flow in open nanosystems, revealing transient excited state activity indicative of Coulomb blockade effects.

Contribution

It introduces a method to analyze transient electron dynamics in nanosystems considering Coulomb interactions using generalized master equations and exact diagonalization.

Findings

Excited states are more active than the ground state during transients.

Coulomb blockade manifests as dynamical signatures in transient regimes.

Different sample models show consistent Coulomb interaction effects.

Abstract

We obtain and analyze the effect of electron-electron Coulomb interaction on the time dependent current flowing through a mesoscopic system connected to biased semi-infinite leads. We assume the contact is gradually switched on in time and we calculate the time dependent reduced density operator of the sample using the generalized master equation. The many-electron states (MES) of the isolated sample are derived with the exact diagonalization method. The chemical potentials of the two leads create a bias window which determines which MES are relevant to the charging and discharging of the sample and to the currents, during the transient or steady states. We discuss the contribution of the MES with fixed number of electrons N and we find that in the transient regime there are excited states more active than the ground state even for N=1. This is a dynamical signature of the Coulomb blockade phenomenon. We discuss numerical results for three sample models: short 1D chain, 2D lattice, and 2D parabolic quantum wire.