Large S approach to the frustrated Heisenberg model for CaV4O9: Commensurate spin configurations and quantum fluctuations

Three kinds of classical spin configurations relevant to the frustrated Heisenberg model for CaV4O9 are obtained, These configurations are characterized by the wave vectors (0;0), (pi, 0) and (pi, pi): respectively, Especially, the configuration with (pi; 0), which is stabilized when next nearest neighbor couplings are strong enough, is not the four-sublattice Neel structure. Spin-wave calculations around these configurations are carried out to estimate the magnitude of quantum fluctuations in the case of S = 1/2 and ground state phase diagrams are presented.