Critical properties of the double-frequency sine-Gordon model with applications

We study the properties of the double-frequency sine-Gordon model in the vi cinity of the Ising quantum phase transition displayed by this model. Using a mapping onto a generalized lattice quantum Ashkin-Teller model, we obtai n critical and nearly-off-critical correlation functions of various operato rs. We discuss applications of the double-sine-Gordon model to one-dimensio nal physical systems, like spin chains in a staggered external field and in teracting electrons in a staggered potential. (C) 2000 Elsevier Science B.V . All rights reserved.