Ferromagnetism in the SU(N) Kondo lattice model -- SU(N) double exchange and supersymmetry

TL;DR

This paper investigates the ground-state phases of the SU(N) Kondo-lattice model in one dimension, revealing insulating and ferromagnetic phases, and explores supersymmetry realizations in cold atom systems.

Contribution

It extends the understanding of the SU(N) Kondo-lattice model by identifying its insulating and ferromagnetic phases and generalizing the double-exchange mechanism to SU(N).

Findings

Identified two insulating phases, including an SU(N) analogue of the gapped Kondo singlet.

Proved the ground state is ferromagnetic in low- or high-density regimes depending on J_K.

Discussed possible realization of SU(N|1) supersymmetry in cold atom systems.

Abstract

We study the ground-state properties of the SU(N)-generalization of the Kondo-lattice model in one dimension when the Kondo coupling J_K (both ferromagnetic and antiferromagnetic) is sufficiently strong. Both cases can be realized using alkaline-earth-like cold gases in optical lattices. Specifically, we first carry out the strong-coupling expansion and identify two insulating phases (one of which is the SU(N)-analogue of the well-known gapped Kondo singlet phase). We then rigorously establish that the ground state in the low-density (for J_K<0) or the high-density (for J_K>0) region is ferromagnetic. The results are accounted for by generalizing the double-exchange mechanism to SU(N) "spins". Possible realizations of Bose-Fermi supersymmetry SU(N|1) in the (generalized) SU(N) Kondo-lattice model are discussed as well.