Phase diagram of the Bose Kondo-Hubbard model

TL;DR

This paper investigates the phase diagram of a bosonic Kondo-Hubbard model in optical lattices, revealing a first-order superfluid to Mott insulator transition influenced by magnetic fluctuations and lattice separability constraints.

Contribution

It introduces a bosonic Kondo-Hubbard model with analysis of phase transitions, highlighting the role of quantum spin fluctuations and lattice geometry in quantum simulation.

Findings

Superfluid to Mott insulator transition is accompanied by a magnetic transition.

Quantum spin fluctuations induce a first-order phase transition.

Lattice separability constrains quantum simulation proposals.

Abstract

We study a bosonic version of the Kondo lattice model with an on-site repulsion in the conduction band, implemented with alkali atoms in two bands of an optical lattice. Using both weak and strong-coupling perturbation theory, we find that at unit filling of the conduction bosons the superfluid to Mott insulator transition should be accompanied by a magnetic transition from a ferromagnet (in the superfluid) to a paramagnet (in the Mott insulator). Furthermore, an analytic treatment of Gutzwiller mean-field theory reveals that quantum spin fluctuations induced by the Kondo exchange cause the otherwise continuous superfluid to Mott-insulator phase transition to be first order. We show that lattice separability imposes a serious constraint on proposals to exploit excited bands for quantum simulations, and discuss a way to overcome this constraint in the context of our model by using an experimentally realized non-separable lattice. A method to probe the first-order nature of the transition based on collapses and revivals of the matter-wave field is also discussed.