Phase transitions of a 2D deformed-AKLT model

TL;DR

This paper investigates the phase diagram of a 2D spin-2 deformed-AKLT model, revealing Néel, XY, and AKLT phases, and explores the effects of a factorizable point using tensor-network methods.

Contribution

It provides a detailed tensor-network analysis of the phase transitions and new phases in a 2D deformed-AKLT model, including the discovery of an XY phase and large correlation length regions.

Findings

Confirmed the Néel phase in the model.

Identified an XY phase with quasi-long-range order.

Discovered a large correlation length region near the AKLT phase.

Abstract

We study spin-2 deformed-AKLT models on the square lattice, specifically a two-parameter family of $O(2)$-symmetric ground-state wavefunctions as defined by Niggemann, Kl\"umper, and Zittartz, who found previously that the phase diagram consists of a N\'eel-ordered phase and a disordered phase which contains the AKLT point. Using tensor-network methods, we not only confirm the N\'eel phase but also find an XY phase with quasi-long-range order and a region adjacent to it, within the AKLT phase, with very large correlation length, and investigate the consequences of a perfectly factorizable point at the corner of that phase.