The spin gap of CaV4O9 revisited

TL;DR

This paper revisits the spin gap in CaV4O9 using extensive exact diagonalizations, confirming a large-plaquette phase and clarifying the exchange interactions needed to match neutron scattering data.

Contribution

It provides a detailed analysis of the large-plaquette phase in CaV4O9 and clarifies the exchange interactions consistent with experimental data.

Findings

Confirmation of a large-plaquette phase across a wide parameter range

Neutron data require a dominant intra-plaquette second neighbor exchange

Justification of perturbative calculations for neutron scattering interpretation

Abstract

The large-plaquette scenario of the spin gap in CaV4O9 is investigated on the basis of extensive exact diagonalizations. We confirm the existence of a large-plaquette phase in a wide range of parameters, and we show that the most recent neutron scattering data actually require an intra-plaquette second neighbor exchange integral much larger than the inter-plaquette one, thus justifying the perturbative calculation used in the interpretation of the neutron scattering experiments.