Multipolar Kondo Effect in $^1$S$_0$-$^3$P$_2$ Mixture of $^{173}$Yb Atoms

TL;DR

This paper investigates the multipolar Kondo effect in a cold Fermi gas of $^{173}$Yb atoms, revealing enhanced Kondo temperature, complex exchange interactions, and indications of a non-Fermi liquid phase through RG analysis.

Contribution

It introduces a theoretical framework for multipolar Kondo interactions in cold Yb atoms, including RG analysis and fixed points, highlighting non-Fermi liquid behavior.

Findings

Enhanced Kondo temperature due to multipolar interactions

Identification of antiferromagnetic exchange mechanisms

Evidence of over-screening and non-Fermi liquid phase

Abstract

Whereas in the familiar Kondo effect the exchange interaction is dipolar, it can also be multipolar, as has been realized in a recent experiment. Here we study multipolar Kondo effect in a Fermi gas of cold $^{173}$Yb atoms. Making use of different AC polarizability of the electronic ground state Yb($^{1}$S$_{0}$) and the long-lived metastable state Yb$^{*}$($^{3}$P$_{2}$), it is suggested that the latter atoms can be localized and serve as a dilute concentration of magnetic impurities while the former ones remain itinerant. The exchange mechanism between the itinerant Yb and the localized Yb$^{*}$ atoms is analyzed and shown to be antiferromagnetic. The quadruple and octuple interactions act to enhance the Kondo temperature $T_K$ that is found to be experimentally accessible. The bare exchange Hamiltonian needs to be decomposed into dipole ($d$), quadruple ($q$) and octuple ($o$) interactions in order to retain its form under renormalization group (RG) analysis, in which the corresponding exchange constants ($\lambda_{\mathrm{d}}$, $\lambda_{\mathrm{q}}$ and $\lambda_{\mathrm{o}}$) flow independently. Numerical solution of the RG scaling equations reveals a few finite fixed points, indicating an over-screening, which suggests a non-Fermi liquid phase. The impurity contribution to the magnetic susceptibility is calculated in the weak coupling regime (${T}\gg{T}_{K}$).