Loop-Cluster Simulation of the $t$-$J$ Model on the Honeycomb Lattice
  Inspired by the lattice structure of the unhydrated variant of the superconducting material Na$_x$CoO$_2 \cdot$yH$_2$O at $ x = {1/3}$, we study the $t$-$J$ model on a honeycomb lattice by using an efficient loop-cluster algorithm. The low-energy physics of the undoped system and of the single hole sector is described by a systematic low-energy effective field theory. The staggered magnetization per spin $\widetilde{{\cal M}}_s = 0.2688(3)$, the spin stiffness $\rho_s = 0.102(2) J$, the spin wave velocity $c= 1.297(16) J a$, and the kinetic mass $M'$ of a hole are obtained by fitting the numerical Monte Carlo data to the effective theory predictions. 
F.-J. Jiang, F. K\"ampfer, M. Nyfeler, and U.-J. Wiese