Quantum correlations in a few-atom spin-1 Bose-Hubbard model

We study the thermal quantum correlations and entanglement in the spin-1 Bose-Hubbard model with two and three particles. While we use negativity to calculate entanglement, more general non-classical correlations are quantified using a new measure based on a necessary and sufficient condition for the zero-discord state. We demonstrate that the energy level crossings in the ground state of the system are signaled by both the behavior of thermal quantum correlations and entanglement.