Phase Effects on the Conductance Through Parallel Double Dots

TL;DR

This paper investigates how magnetic flux and charge states influence quantum conductance and phase coherence in a double-dot ring system, revealing conditions for Kondo regimes and circulating currents.

Contribution

It introduces a detailed analysis of phase effects on conductance in double-dot systems, highlighting the role of magnetic flux and charge states in controlling quantum interference and Kondo phenomena.

Findings

Dephasing leads to different Kondo regimes depending on flux and charge.

Circulating currents can exist without magnetic flux, based on system parameters.

Magnetic flux influences the phase and conductance behavior in double-dot rings.

Abstract

Phase effects on the conductance of a double-dot system in a ring structure threaded by a magnetic flux are studied. The Aharonov-Bohm effect combined with the dot many-body charging effects determine the phases of the currents going through each arm of the ring. The cases for zero magnetic flux or half a quantum of flux are discussed in detail. It is shown that, depending upon the magnetic flux and the state of charge of the dots, controlled by gate potentials, the dephasing of the upper and lower arm current gives rise to a $S=1/2$ or S=1 Kondo regime. We also show that even in the absence of a magnetic flux there can be a circulating current in the ring, depending on the system parameters.