Observation of the SU(4) Kondo state in a double quantum dot

TL;DR

This paper reports the experimental realization of an SU(4) Kondo state in a double quantum dot system, demonstrating detailed control over spin and orbital interactions through transport measurements and numerical calculations.

Contribution

It introduces a novel double quantum dot setup that enables orbital and spin-resolved spectroscopy of the SU(4) Kondo effect, advancing understanding of quantum impurity models.

Findings

Successful observation of the SU(4) Kondo state.

Capacitive coupling allows orbital-resolved bias spectroscopy.

Device provides detailed control over spin and orbital physics.

Abstract

Central to condensed matter physics are quantum impurity models, which describe how a local degree of freedom interacts with a continuum. Surprisingly, these models are often universal in that they can quantitatively describe many outwardly unrelated physical systems. Here we develop a double quantum dot-based experimental realization of the SU(4) Kondo model, which describes the maximally symmetric screening of a local four-fold degeneracy. As demonstrated through transport measurements and detailed numerical renormalization group calculations, our device affords exquisite control over orbital and spin physics. Because the two quantum dots are coupled only capacitively, we can achieve orbital state- or "pseudospin"-resolved bias spectroscopy, providing intimate access to the interplay of spin and orbital Kondo effects. This cannot be achieved in the few other systems realizing the SU(4) Kondo state.