Non-monotonic field dependence of Kondo conductance in a single-electron transistor driven by microwave field

TL;DR

This paper proposes a phenomenological model explaining the non-monotonic magnetic field dependence of Kondo conductance in a single-electron transistor under microwave irradiation, matching experimental observations and suggesting new experimental directions.

Contribution

It introduces a mechanism where microwave-induced spin-flip resonance explains the observed conductance features, advancing understanding of Kondo effects under dynamic conditions.

Findings

Qualitative explanation of non-monotonic conductance dependence

Identification of microwave frequency matching Zeeman energy as key

Prediction of dynamic response in out-of-equilibrium devices

Abstract

The interplay between magnetic field and microwave applied in a single-electron transistor(SET) has a profound influence on the Kondo effect, as shown in a recent experiment[B. Hemingway, S. Herbert, M. Melloch and A. Kogan, arXiv:1304.0037(2013)]. For a given microwave frequency, the Kondo differential conductance shows a non-monotonic magnetic field dependence, and a very sharp peak is observed for certain field applied. Additionally, the microwave frequency is found to be larger of about one order than the corresponding Zeeman energy. These two features are not understood in the current theory. Here we propose a phenomenological mechanism to explain these observations. When both magnetic field and microwave are applied in the SET, if the frequency matches the (renormalized) Zeeman energy, it is assumed that the microwave is able to induce spin-flip in the SET, which leads to two consequences. One is the dot level shifts down and the other is the renormalization of the Zeeman energy. This picture can not only explain qualitatively the main findings in the experiment but also further stimulate the related experimental study of the dynamic response of the Kondo effect in out-of-equilibrium devices.