A sign-free quantum Monte Carlo study of the triangular-lattice antiferromagnetic XXZ model near the Ising limit

The materials K2CoSe2O6 and Na2BaCo(PO4)2 have both been recently analyzed through an antiforremnagtic (AFM) XXZ model on the triangular lattice. When the model is close to the Ising limit, it reduces to a specific quantum dimer model on the honeycomb lattice. Although the AFM XXZ model suffers from a well-known sign problem, the quantum dimer model can be studied with sign-problem-free quantum Monte Carlo. As is common for quantum dimer models, we include the corresponding Rokhsar-Kivelson term and study the finite-temperature phase diagram. We connect our results with the materials ane relevant experiments.