Smearing of charge fluctuations in a grain by spin-flip assisted tunneling

TL;DR

This paper studies how charge fluctuations in a quantum dot system are affected by spin-flip processes, revealing a stable SU(4) Kondo fixed point that smooths Coulomb staircase features, with potential experimental implications.

Contribution

It demonstrates the emergence of a stable SU(4) Kondo fixed point due to entangled charge and spin flips in a quantum dot system, affecting charge fluctuation behavior.

Findings

Charge fluctuations are significantly smeared out by spin-flip processes.

A stable SU(4) Kondo fixed point is identified.

The effects are robust and observable experimentally.

Abstract

We investigate the charge fluctuations of a grain (large dot) coupled to a lead via a small quantum dot in the Kondo regime. We show that the strong entanglement of charge and spin flips in this setup can result in a stable SU(4) Kondo fixed point, which considerably smears out the Coulomb staircase behavior already in the weak tunneling limit. This behavior is robust enough to be experimentally observable.