Frustrated antiferromagnetic quantum spin chains for spin length S > 1

TL;DR

This study uses DMRG to analyze frustrated antiferromagnetic quantum spin chains with S=3/2 and S=2, revealing disorder points, Lifshitz points, and the disappearance of free end spins, highlighting new quantum phenomena in higher spin chains.

Contribution

It demonstrates the existence and disappearance of free end spins in higher S chains and links quantum disorder points to classical phase transitions, extending previous findings for S=1.

Findings

Disorder and Lifshitz points are localized.

Free end spins S'=[S/2] are observed and then vanish.

First order transition for S=1 is generalized to S>1/2.

Abstract

We investigate frustrated antiferromagnetic Heisenberg quantum spin chains at T=0 for S=3/2 and S=2 using the DMRG method. We localize disorder and Lifshitz points, confirming that quantum disorder points can be seen as quantum remnants of classical phase transitions. Both in the S=3/2 and the S=2 chain, we observe the disappearance of effectively free S=1/2 and S=1 end spins respectively. The frustrated spin chain is therefore a suitable system for clearly showing the existence of free end spins S'=[S/2] also in half-integer antiferromagnetic spin chains with S>1/2. We suggest that the first order transition found for S=1 in our previous work is present in all frustrated spin chains with S>1/2, characterized by the disappearance of effectively free end spins with S'=[S/2].