Modified Perturbation Theory Applied to Kondo-Type Transport through a Quantum Dot under a Magnetic Field

TL;DR

This paper applies a modified perturbation theory to analyze the linear conductance of a quantum dot under a magnetic field, revealing how conductance is affected by magnetic field and electron-hole asymmetry.

Contribution

It introduces a modified perturbation approach that accurately reproduces atomic limit and Friedel sum rule for quantum dot conductance calculations under magnetic fields.

Findings

Conductance near electron-hole symmetry is suppressed by magnetic field at low temperatures.

Positive magnetoconductance occurs with large electron-hole asymmetry.

Method extends second-order perturbation theory to finite temperatures approximately.

Abstract

Linear conductance through a quantum dot is calculated under a finite magnetic field using the modified perturbation theory. The method is based on the second-order perturbation theory with respect to the Coulomb repulsion, but the self-energy is modified to reproduce the correct atomic limit and to fulfill the Friedel sum rule exactly. Although this method is applicable only to zero temperature in a strict sense, it is approximately extended to finite temperatures. It is found that the conductance near electron-hole symmetry is suppressed by the application of the magnetic field at low temperatures. Positive magnetoconductance is observed in the case of large electron-hole asymmetry.