GROUND-STATES OF COUPLED DOUBLE-CHAIN MODELS

A classical model consisting of two chains coupled in a ladder configuration with interactions between all adjacent atoms is considered. It is shown that the ground states can be obtained from a model with a single chain of pseudoparticles in an external substrate potential and with new effective interactions between adjacent pseudoparticles. When the original interactions are either everywhere convex or Lennard-Jones like, the ground-state behavior can be understood by considering a simpler analytic model with Lennard-Jones interactions between adjacent atoms. In the ground-state phase diagram, not only are the expected pinched phases found but dimerized phases and an infinite series of superdegenerate points accumulating at a multiphase point, the end point of an accumulation line, are seen. The variation of the linear density is discussed in terms of measurable quantities. Finally, the effects of other forms of the interparticle potentials are considered and the relevance to one-dimensional liquid crystals and other physical systems is discussed. © 1990 The American Physical Society.