Onset of incommensurability in quantum spin chains

TL;DR

This paper investigates the emergence of incommensurability and minimal correlation length at valence-bond-solid points in quantum spin chains, proposing a mechanism that explains these phenomena and can be generalized.

Contribution

It introduces a new theoretical mechanism explaining incommensurability onset and correlation length behavior at VBS-like points in quantum spin chains.

Findings

Incommensurability occurs near VBS points.

Correlation length is shortest at VBS points.

Correlation functions decay exponentially at VBS points.

Abstract

In quantum spin chains, it has been observed that the incommensurability occurs near valence-bond-solid (VBS)-type solvable points, and the correlation length becomes shortest at VBS-type points. Besides, the correlation function decays purely exponentially at VBS-type points, in contrast with the two-dimensional (2D) Ornstein-Zernicke type behavior in the other region with an excitation gap. We propose a mechanism to explain the onset of the incommensurability and the shortest correlation length at VBS-like points. This theory can be applicable for more general cases.