Plaquette order in the J1-J2-J3 model: Series expansion analysis

ARLEGO MARCELO, BRENIG WOLFRAM

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

Año: 2008 vol. 78 p. 224415 - 224420

0163-1829

Series expansion based on the flow equation method is employed to study the zero-temperature properties of the spin-1/2 J1-J2-J3 antiferromagnet in two dimensions. Starting from the exact limit of decoupled plaquettes in a particular generalized J1-J2-J3 model, we analyze the evolution of the ground-state energy and the elementary triplet excitations in powers of all three interplaquette couplings up to fifth order. We find that the plaquette phase remains stable over a wide range of exchange couplings and connects adiabatically up to the case of the plain J1-J2-J3 model but not to the J1-J2 model at J3=0. Besides confirming the existence of such a phase, recently predicted by Mambrini et al. [Phys. Rev. B 74, 144422 (2006)], we estimate its extent by Dlog-Padé analysis of the critical lines that result from closure of the triplet gap.