On some upper bounds for spin velocity and instability of gapless state of 1-d Heisenberg chains

TL;DR

This paper derives upper bounds for spin velocity in half-integer-spin Heisenberg chains and links these bounds to the instability of the gapless state, especially in frustrated systems.

Contribution

It introduces new upper bounds for spin velocity and connects them to the instability phenomena in frustrated quantum spin chains.

Findings

Upper bounds for spin velocity are established.

The instability of the gapless state is characterized.

Frustrated systems exhibit these instability features.

Abstract

We derive upper bounds for spin velocity in half-integer-spin Heisenberg antiferromagnetic chains. We relate these upper bounds to the instability of the gapless state, which is observed in frustrated systems.