Anti-Kondo regime of charge transport through a double dot molecule

TL;DR

This paper investigates charge transport in a double quantum dot system with strong inter-dot tunneling, revealing an anti-Kondo regime where conductance remains high due to orbital interference effects.

Contribution

It introduces the concept of an anti-Kondo regime in double dot molecules and explains the persistent high conductance through interference effects.

Findings

Kondo peaks observed for 1 or 3 electrons

Constant non-zero conductance for 2 electrons

Interplay of orbitals causes anti-Kondo behavior

Abstract

The conductance through a serial double dot structure for which the inter-dot tunneling is stronger than the tunneling to the leads is studied using the numerical density matrix renormalization group method and analytic arguments. When the dots are occupied by 1 or 3 electrons the usual Kondo peak is obtained. For the case in which 2 electrons occupy the molecule a singlet is formed. Nevertheless, the conductance in that case has a constant non-zero value, and might even be equal to the maximum conductance of $2 e^2/h$ for certain values of the molecule parameters. We show that this is the result of the subtle interplay between the symmetric and anti-symmetric orbitals of the molecule caused by interactions and interference.