Continuous phase transition between Neel and valence bond solid phases in a J-Q-like spin ladder system

TL;DR

This paper studies a quantum phase transition between Neel and VBS phases in a spin ladder system, showing it is continuous and belongs to the Gaussian universality class with specific critical exponents.

Contribution

It introduces a one-dimensional J-Q-like model and provides evidence that the Neel-VBS transition is continuous and Gaussian, with consistent critical exponents.

Findings

The transition is continuous and Gaussian in nature.

Critical exponents satisfy Gaussian universality class constraints.

Exponents remain stable along the phase boundary.

Abstract

We investigate a quantum phase transition between a Neel phase and a valence bond solid (VBS) phase, in each of which a different Z2 symmetry is broken, in a spin-1/2 two-leg XXZ ladder with a four-spin interaction. The model can be viewed as a one-dimensional variant of the celebrated J-Q model on a square lattice. By means of variational uniform matrix product state calculations and an effective field theory, we determine the phase diagram of the model, and present evidences that the Neel-VBS transition is continuous and belongs to the Gaussian universality class with the central charge c=1. In particular, the critical exponents $\beta, \eta,$ and, $\nu$ are found to satisfy the constraints expected for a Gaussian transition within numerical accuracy. These exponents do not detectably change along the phase boundary while they are in general allowed to do so for the Gaussian class.