Quantum phase transition in the Plaquette lattice with anisotropic spin exchange

Abstract

I study the influence of anisotropic spin exchange on a quantum phase transition in the Plaquette lattice driven by the purely quantum effect of singlet formation. I study the influence of i) a Dzyaloshinskii-Moriya exchange and ii) four spin exchange on the transition point by evaluating spin-spin correlations and the spin gap with exact diagonalization. The results point to a stabilization of the Néel-like long range order when the Dzyaloshinskii-Moriya exchange is added, whereas the four-spin exchange might stabilize the singlet order as well as the Néel-like order depending on its strength. quantum antiferromagnets, Plaquette lattice, anisotropic spin exchange PACS: 75.10.Jm, 75.50.Ee, 75.40.Mg