Eur. Phys. J. B 35, 465-473 (2003)
https://doi.org/10.1140/epjb/e2003-00299-7

On c = 1 critical phases in anisotropic spin-1 chains

¹ INFM Research Unit of Bologna, 6/2 v.le B. Pichat, 40127 Bologna Italy
² Physics Department, University of Bologna, and INFN, 6/2 v.le B. Pichat, 40127 Bologna, Italy

Corresponding author: ^a roncaglia@bo.infn.it

Received: 16 July 2003
Published online: 24 October 2003

Abstract

Quantum spin-1 chains may develop massless phases in presence of Ising-like and single-ion anisotropies. We have studied c=1 critical phases by means of both analytical techniques, including a mapping of the lattice Hamiltonian onto an O(2) NLσM, and a multi-target DMRG algorithm which allows for accurate calculation of excited states. We find excellent quantitative agreement with the theoretical predictions and conclude that a pure Gaussian model, without any orbifold construction, describes correctly the low-energy physics of these critical phases. This combined analysis indicates that the multicritical point at large single-ion anisotropy does not belong to the same universality class as the Takhtajan-Babujian Hamiltonian as claimed in the past. A link between string-order correlation functions and twisting vertex operators, along the c=1 line that ends at this point, is also suggested.