Correlation and symmetry effects in transport through an artificial molecule

TL;DR

This paper investigates how correlation effects, symmetry, and interdot tunneling influence transport properties in an artificial diatomic molecule, revealing selection rules and symmetry-dependent conductance behaviors consistent with experimental observations.

Contribution

It introduces a detailed model incorporating correlations, symmetry, and tunneling in double quantum dot systems, elucidating their impact on spectral weights and transport characteristics.

Findings

Interdot tunneling significantly shapes eigenstates and spectral weights.

Symmetry influences I-V characteristics, aligning with experimental data.

Most states contribute minimally to current at finite bias.

Abstract

Spectral weights and current-voltage characteristics of an artificial diatomic molecule are calculated, considering cases where the dots connected in series are in general different. The spectral weights allow us to understand the effects of correlations, their connection with selection rules for transport, and the role of excited states in the experimental conductance spectra of these coupled double dot systems (DDS). An extended Hubbard Hamiltonian with varying interdot tunneling strength is used as a model, incorporating quantum confinement in the DDS, interdot tunneling as well as intra- and interdot Coulomb interactions. We find that interdot tunneling values determine to a great extent the resulting eigenstates and corresponding spectral weights. Details of the state correlations strongly suppress most of the possible conduction channels, giving rise to effective selection rules for conductance through the molecule. Most states are found to make insignificant contributions to the total current for finite biases. We find also that the symmetry of the structure is reflected in the I-V characteristics, and is in qualitative agreement with experiment.