Free energy of the three-dimensional spin-1/2 quantum heisenberg model to O[T-6]

摘要

By applying the Friedberg-Lee-Ren's theorem (Ann. Phys, (N.Y.) 228, 52 (1993)) to the spin-1/2 three-dimensional isotropic quantum Heisenberg system, we obtain the low-temperature expansion of the free energy through a field theoretical calculation done in the equivalent lattice boson system. We reproduced Dyson's result and also extended it from T-5 to T-6. Nevertheless, because of the peculiar property of the spin operator being neither bosonic nor fermionic, the extension is not easy to obtain by other method. (C) 2001 Academic Press. [References: 11]