Abstract
The excitation spectrum of the antiferromagnetic spin-1/2 Heisenberg Hamiltonian H=tsumJS⋅S on L×L lattices is evaluated by a projector quantum Monte Carlo method. These results suggest that the exact spectrum for the finite lattice is ≃Z(L), for all k, where =4JS √1- with =(cos+cos)/2 is from linear-spin-wave theory. We find Z(L)=+B/, leading to =1.21±0.03 for L=∞. A comparison with experiments on is discussed.
- Received 24 January 1992
DOI:https://doi.org/10.1103/PhysRevB.46.2933
©1992 American Physical Society