Dd. Betts et al., Improved finite-lattice estimates of the properties of two quantum spin models on the infinite square lattice, CAN J PHYS, 77(5), 1999, pp. 353-369
This paper describes an improvement in the method of exact diagonalization
of Hamiltonians of quantum spin models on finite square lattices and the st
atistical analysis of the data so obtained to estimate the physical propert
ies of the models on the infinite square lattices at zero temperature. The
geometry and topology of finite square lattices are described. The models s
tudied are the spin one-half <it>XY</it> and Heisenberg antiferromagnets us
ing 28 finite square lattices with up to 32 vertices. Our estimates of the
energy and magnetization on each model on the infinite lattice at zero temp
erature compare very well with recent estimates using quantum Monte Carlo,
series expansion, and spin wave estimates. Estimates of spin wave velocity
and transverse susceptibilities are more scattered.