Ground-state properties of the spin-1/2 antiferromagnetic Heisenberg
model on the triangular lattice: A variational study based on
entangled-plaquette states
We study, on the basis of the general entangled-plaquette variational ansatz,
the ground-state properties of the spin-1/2 antiferromagnetic Heisenberg model
on the triangular lattice. Our numerical estimates are in good agreement with
available exact results and comparable, for large system sizes, to those
computed via the best alternative numerical approaches, or by means of
variational schemes based on specific (i.e., incorporating problem dependent
terms) trial wave functions. The extrapolation to the thermodynamic limit of
our results for lattices comprising up to N=324 spins yields an upper bound of
the ground-state energy per site (in units of the exchange coupling) of
−0.5458(2) [−0.4074(1) for the XX model], while the estimated
infinite-lattice order parameter is 0.3178(5) (i.e., approximately 64% of the
classical value).Comment: 8 pages, 3 tables, 2 figure