title: Order-disorder quantum phase transition in the quasi-one-dimensional spin-1/2 collinear antiferromagnetic Heisenberg model.
abstract: The ground-state properties of the quasi-one-dimensional spin-1/2 antiferromagnetic Heisenberg model is investigated by using a variational method. Spins on chains along the x direction are antiferromagnetically coupled with exchange J>0, while spins between chains in the y direction are coupled either ferromagnetically (J' < 0) or antiferromagnetically (J' > 0). The staggered and the colinear antiferromagnetic magnetizations are computed and their dependence on the anisotropy parameter λ=|J'|/J is analyzed. It is found that an infinitesimal interchain coupling parameter is sufficient to stabilize a long-range order with either a staggered magnetization m_{s} (J' > 0) or a colinear antiferromagnetic magnetization m_{caf} (J' < 0), both behaving as ≃λ¹/² for λ → 0.
authors.affiliation: Departamento de Física, Universidade Federal de Minas Gerais, CP 702, Belo Horizonte - Minas Gerais, 30161-970, Brazil.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Rufo
authors.forename: Griffith
authors.initials: G
authors.lastname: Mendonça
authors.forename: J A
authors.initials: JA
authors.lastname: Plascak
authors.forename: J Ricardo
authors.initials: JR
authors.lastname: de Sousa