Doping of a spin-1 chain: integrable model

TL;DR

This paper constructs an exactly solvable model for a doped spin-1 antiferromagnetic chain, revealing how doping introduces new excitations and affects the gapless modes, with implications for understanding quantum spin chains.

Contribution

It presents a novel integrable model for doped spin-1 chains, analyzing the effects of doping on the low-energy excitations and the Haldane gap.

Findings

Doping introduces a scalar charge field and a singlet Majorana fermion.

The gapless triplet of Majorana fermions persists with doping.

The model remains integrable and exactly solvable.

Abstract

An exactly soluble model describing a spin S=1 antiferromagnetic chain doped with mobile S=1/2 carriers is constructed. In its continuum limit the undoped state is described by three gapless Majorana fermions composing the SU(2) triplet. Doping adds to this a scalar charge field and a singlet Majorana fermion with different velocity. We argue that this mode survives when the Haldane gap is added.