Extension of the Method of Exact Diagonalization of Quantum Spin Models to Finite Face Centred Cubic Lattices and Estimation of the T=0 Properties of the S= 1/2 XY Ferromagnet on the Infinite fcc Lattice

抄録

First we introduce the upper triangular lattice form method that permits one to derive easily the complete set of finite lattices of any given number, N, of vertices for any regular infinite lattice in any number of dimensions, and we use it to obtain all finite fcc lattices of N<28. We compute the ground state energy, magnetization and spin-spin correlations of the spin one-half XY ferromagnet on each of these lattices. Extrapolation of these data to infinite N yields T=0 estimates of the properties mentioned. Our estimates agree to a few tenths of a percent with spin wave, series expansion and variational estimates.