Coherent exchange-coupled nonlocal Kondo impurities

TL;DR

This paper explores how electronic cavity modes in double quantum dots influence magnetic impurity interactions, revealing new phases like 'cat Kondo' and providing insights into nonlocal magnetic impurity behavior.

Contribution

It introduces a novel cavity-mediated interaction mechanism in double-dot systems and identifies new many-body phases, including the 'cat Kondo' state.

Findings

Kondo can dominate on individual dots

Cavity mediates nonlocal singlet or 'cat Kondo' phases

Identifies quantum phase transitions between states

Abstract

Quantum dots exhibit a variety of strongly correlated effects, e.g., when tuned to emulate localized magnetic impurities that form a Kondo singlet with their surrounding environment. Interestingly, in double-dots setups, the magnetic impurities couple to each other by direct Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, which wins over the Kondo physics. In this work, we investigate a double-dot device where the dots are coupled via off-resonant ballistic whispering gallery modes, dubbed electronic cavity modes. Within this cavity-double-dot system, we study, using variational matrix product state techniques, the competition between Kondo formation and the coherent RKKY-like interaction that the cavity facilitates. Specifically, we find that (i) Kondo can win and form on each dot individually, or (ii) the cavity can win and mediate between the two dots either a singlet or a novel nonlocal Kondo-like effect phase, which we call "cat Kondo". We systematically study the quantum phase transitions between the different many-body states. Our discoveries lay the foundation for the experimental observation of unconventional nonlocal magnetic impurities.