Critical theory of the topological quantum phase transition in a spin-2 chain

TL;DR

This paper investigates the phase diagram of a spin-2 chain, revealing a critical line with central charge 5/2 described by SO(5)_1 WZW theory, and confirms a dimer phase in the AKLT--SZH model.

Contribution

It identifies a critical line with specific conformal field theory description in the phase diagram of a spin-2 chain, advancing understanding of topological quantum phase transitions.

Findings

Presence of a dimer phase in the AKLT--SZH model

Critical line with central charge c=5/2

Description by SO(5)_1 WZW conformal field theory

Abstract

We systematically study the phase diagram of S=2 spin chain, by means of density-matrix renormalization group and exact diagonalization methods and confirm the presence of a dimer phase in the AKLT--SZH model. We find that the whole phase boundary between the dimer and SZH phases, including the multicritical point, is a critical line with the same central charge $c=5/2$. Finally, we propose and confirm that this line can be described by the $\rm SO(5)_1$ Wess-Zumino-Witten (WZW) conformal field theory.