A general CFT model for antiferromagnetic spin-1/2 ladders with Mobius boundary conditions

TL;DR

This paper develops a conformal field theory framework to describe the low-energy properties of antiferromagnetic spin-1/2 ladders with Mobius boundary conditions, highlighting topological defects and excitation spectra.

Contribution

It introduces a general CFT model for spin-1/2 ladders with Mobius boundary conditions, extending previous methods to include topological defects and boundary effects.

Findings

CFT with central charge c=2 describes the model's low-energy behavior.

Mobius boundary conditions induce topological defects and non-trivial excitations.

Analysis of perturbations reveals RG flow from the UV critical point.

Abstract

We show how the low-energy properties of the 2-leg XXZ spin-1/2 ladders with general anisotropy parameter $\Delta $ on closed geometries can be accounted for in the framework of the m-reduction procedure developed in [1]. In the limit of quasi-decoupled chains, a conformal field theory (CFT) with central charge c=2 is derived and its ability to describe the model with different boundary conditions is shown. Special emphasis is given to the Mobius boundary conditions which generate a topological defect corresponding to non trivial single-spinon excitations. Then, in the case of the 2-leg XXX ladders we discuss in detail the role of various perturbations in determining the renormalization group flow starting from the ultraviolet (UV) critical point with c=2.