Disordered ground states in a quantum frustrated spin chain with side chains

TL;DR

This paper investigates a complex quantum spin chain with side chains, revealing two disordered spin-gap phases and proposing a singlet cluster solid model based on various analytical and numerical methods.

Contribution

It introduces a nonlinear sigma model approach and a detailed phase diagram for a frustrated mixed spin chain with side chains, highlighting novel disordered phases.

Findings

Identified two disordered spin-gap phases in the model.

Proposed a singlet cluster solid ground state picture.

Validated the phases using numerical, perturbational, and variational methods.

Abstract

We study a frustrated mixed spin chain with side chains, where the spin species and the exchange interactions are spatially varied. A nonlinear sigma model method is formulated for this model, and a phase diagram with two disordered spin-gap phases is obtained for typical cases. Among them we examine the case with a main chain consisting of an alternating array of spin-1 and spin-1/2 sites and side chains each of a single spin-1/2 site in great detail. Based on numerical, perturbational, and variational approaches, we propose a singlet cluster solid picture for each phase, where the ground state is expressed as a tensor product of local singlet states.