Spin Gap in Two-Dimensional Heisenberg Model for CaV4O9
نویسندگان
چکیده
ABSTRACT: We investigate the mechanism of spin gap formation in a two-dimensional model relevant to Mott insulators such as CaV4O9. From the perturbation expansion and quantum Monte Carlo calculations, the origin of the spin gap is ascribed to the four-site plaquette singlet in contrast to the dimer gap established in the generalized dimerized Heisenberg model. We investigate the mechanism of spin gap formation in a two-dimensional model relevant to Mott insulators such as CaV4O9. From the perturbation expansion and quantum Monte Carlo calculations, the origin of the spin gap is ascribed to the four-site plaquette singlet in contrast to the dimer gap established in the generalized dimerized Heisenberg model.
منابع مشابه
ar X iv : c on d - m at / 9 60 90 73 v 1 7 S ep 1 99 6 Determination of Exchange Parameters for CaV 4 O
Magnetic susceptibility measured for CaV4O9 is analyzed by a method with high temperature expansion. The analysis is consistent with the g-value which is close to 2 and is observed by an ESR experiment. Four exchange parameters in a two-dimensional Heisenberg model are determined to represent CaV4O9. All the exchange parameters are about 500 K and strongly frustrated. The observed spin gap orig...
متن کاملO ct 1 99 5 Spin Gap of Two - Dimensional Antiferromagnet Representing CaV 4 O 9 Kazuhiro Sano and Ken ’ ichi Takano
We examined a two-dimensional Heisenberg model with two kinds of exchange energies, Je and Jc. This model describes localized spins at vanadium ions in a layer of CaV4O9, for which a spin gap is found by a recent experiment. Comparing the high temperature expansion of the magnetic susceptibility to experimental data, we determined the exchange energies as Je ≃ 610 K and Jc ≃ 150 K. By the numer...
متن کاملSpin Gaps in a Frustrated Heisenberg Model for CaV4O9.
I report results of a density matrix renormalization group (DMRG) study of a model for the two dimensional spin-gapped system CaV4O9. This study represents the first time that DMRG has been used to study a two dimensional system on large lattices, in this case as large as 24×11, allowing extrapolation to the thermodynamic limit. I present a substantial improvement to the DMRG algorithms which m...
متن کاملMetaplaquette expansion for the triplet excitation spectrum in CaV4O9
We study antiferromagnetic, S51/2 Heisenberg models with nearestand second-neighbor interactions on the one-fifth depleted square lattice which describes the spin degrees of freedom in the spin-gap system CaV4O9 . The metaplaquette expansion for the triplet excitation spectrum is extended to fifth order, and the results are compared with experimental data on CaV4O9 . We attempt to locate the ph...
متن کاملExact Ground and Excited States of Frustrated Antiferromagnets on the Cav 4 O 9 Lattice
The experimental observation of a spin-gap in the antiferromagnetic spin2 compound CaV4O9 has been attributed to the formation of a plaquette resonating-valence-bond (PRVB) state in the underlying 1/5-depleted square lattice. We construct a spin2 model on the 1/5-depleted lattice for which the PRVB state can be shown to be the exact ground state in a particular parameter regime. In a subspace o...
متن کامل