Non-Haldane Spin Liquid Models with Exact Ground States

TL;DR

This paper introduces a family of exactly solvable spin ladder models that exhibit non-Haldane spin liquid behavior, characterized by unique excitations and phase transitions, expanding understanding of quantum spin liquids.

Contribution

The authors construct new spin ladder models with exact ground states that demonstrate non-Haldane spin liquid properties, including novel excitation spectra and phase transition analysis.

Findings

Elementary excitations are triplet or singlet solitons, not magnons or spinons.

Phase transitions occur between non-Haldane spin liquid, Haldane, and rung-dimer phases.

Models exhibit exact solutions and support non-traditional quantum spin liquid states.

Abstract

We present a family of spin ladder models which admit exact solution for the ground state and exhibit non-Haldane spin liquid properties as predicted recently by Nersesyan and Tsvelik [Phys. Rev. Lett. v.78, 3939 (1997)], and study their excitation spectrum using a simple variational ansatz. The elementary excitation is neither a magnon nor a spinon, but a pair of propagating triplet or singlet solitons connecting two spontaneously dimerized ground states. Second-order phase transitions separate this phase from the Haldane phase and the rung-dimer phase.