Quantum phase transition and conductivity of parallel quantum dots with a moderate Coulomb interaction

V S Protsenko,A A Katanin

doi:10.1088/1742-6596/690/1/012028

Abstract

We study the effects of electronic interactions on transport through parallel quantum dots connected symmetrically to leads, focusing on the case of an intermediate value of the on-site Coulomb interaction at each quantum dot. We apply both the mean-field (MF) approximation and the functional renormalization group (fRG) approach with using the Litim regularization scheme in frequency space to treat the effect of interaction and calculate the energy levels, the magnetization, the square of local spin as well as the linear conductance as a function of gate voltage. Already for intermediate values of the Coulomb interaction, the system exhibits a quantum phase transition from the parallel aligned (high spin state) to the paramagnetic (low spin) regime. This phase transition is accompanied by the appearance of the step discontinuities in the conductance, which can be observed in the experiment.

Highlights

A quantum dot is formed by a nanostructure that restricts the motion of electrons in all three directions
In the article [5] within the numerical renormalization group [6] it has been shown that the strong Coulomb interaction in such geometries leads to the parallel spin alignment state as the ground state of the systems in some range of gate voltages
We focus on the case of an intermediate value of the on-site Coulomb interaction U in each quantum dot, and introduce a weak magnetic field H

Summary

Introduction

A quantum dot is formed by a nanostructure that restricts the motion of electrons in all three directions. We focus on the case of an intermediate value of the on-site Coulomb interaction U in each quantum dot, and introduce a weak magnetic field H. Published under licence by IOP Publishing Ltd energy levels, the magnetization, the square of local spin as well as the linear conductance as function of the gate voltage.

Results

Conclusion