Phase diagram of the bosonic Kondo-Hubbard model

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 strongcoupling 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.

Coherent Heteronuclear Spin Dynamics in an Ultracold Spinor Mixture

“…Using implementations similar to the two-orbital magnetism model originally proposed for alkali-earth atoms [43], but replacing the two orbits with two different kinds of atoms, the bosonic Kondo model [44,45] may be realized. In addition, in analogy to the generation of entanglement with spin-changing interactions in single species spinor condensates [46,47], the inter-species spin-changing interaction can also be used to generate entanglement between distinguishable atoms [48].…”

Confinedp-band Bose-Einstein condensates

“…[23], coherence of p-band atoms in a cubic lattice was indeed demonstrated. Alternatives for suppressing this decay further include loading fermionic atoms into the s band of the lattice [36] or considering experimental setups with nonseparable lattices [19,20,37]. In the first case, the presence of fermions in the s band prevents the bosonic p-band atoms to occupy the lowest band due to atom-atom interactions.…”

Bosonic Kondo-Hubbard model

“…The mobile species occupy an upper band, to which they have been excited through the applicaton of periodic Raman pulses, which allows tunneling. This model was studied in detail with different analytical techniques by Foss-Feig and Rey [14]. In [14], exact results were derived for the small and large interaction limits and the intermediate regime was studied using mean-field theory, for different densities of particles.…”

“…This model was studied in detail with different analytical techniques by Foss-Feig and Rey [14]. In [14], exact results were derived for the small and large interaction limits and the intermediate regime was studied using mean-field theory, for different densities of particles. For one mobile particle per site, they observed a first order transition between a Mott insulator (MI) phase and a superfluid (SF) phase as the interaction is lowered.…”

“…In this paper, we will use exact quantum Monte Carlo simulations to study this bosonic Kondo-Hubbard model [13] and determine exactly the phase diagram and magnetic properties of the system at zero and finite temperatures T and compare with results previously obtained with mean-field approximations [13,14]. In Sec.…”