Charge-Kondo effect mediated by repulsive interactions

TL;DR

This paper explores how capacitive coupling in a double-quantum-dot system can induce a charge-Kondo effect by effectively switching the inter-dot interaction from repulsive to attractive, analyzed through low-energy Hamiltonians and numerical methods.

Contribution

It demonstrates the tunability of the inter-dot interaction via capacitive coupling to a charge-Qubit, leading to different Kondo regimes and providing a detailed theoretical analysis.

Findings

Capacitive coupling reduces and can invert the inter-dot interaction.

System exhibits orbital-Kondo and charge-Kondo behaviors depending on coupling strength.

Thermodynamic and transport properties are characterized using numerical renormalization group.

Abstract

We investigate the Kondo effect in a double-quantum-dot which is capacitively coupled to a charge-Qubit. It is shown that due to this capacitive coupling, the bare inter-dot repulsive interaction in the double-quantum-dot is effectively reduced and eventually changed to an attractive interaction for strong couplings between the double-quantum-dot and the Qubit. By deriving the low-energy effective Hamiltonian of the system, we find that the low energy dynamics of the system corresponding to these two positive or negative effective interaction regimes can be described, respectively, by an isotropic orbital-Kondo or an anisotropic charge-Kondo Hamiltonian. Moreover, we study various thermodynamic and electronic transport properties of the system by using the numerical renormalization group method.