Transition from Haldane Phase to Spin Liquid and Incommensurate Correlation in Spin-1/2 Heisenberg Chains

TL;DR

This paper investigates phase transitions, impurity effects, and incommensurate correlations in the one-dimensional S=1/2 Heisenberg model with dimerization and next-nearest-neighbor interactions, revealing a transition from Haldane phase to spin liquid.

Contribution

It provides a comprehensive phase diagram and analysis of impurity effects and incommensurate correlations in a unified model covering various related systems.

Findings

Transition from Haldane phase to spin liquid in the model

Impurity effects differ between CuGeO3 and Haldane systems

Incommensurate correlations are extensively characterized

Abstract

The bulk properties and impurity effect in the one-dimensional S=1/2 Heisenberg model with dimerization and next-nearest-neighbor exchange are studied by the density matrix renormalization group (DMRG) and exact diagonalization methods. This model widely covers the S=1 Heisenberg model, two-leg ladders, bond-alternating chains and the S=1/2 Heisenberg model. Almost the whole parameter space belongs to the Haldane phase. In the non-dimerizing limit a transition to a kind of spin liquid takes place, characterized by the delocalized spin polarization. This transition causes the distinct impurity effects between a spin-Peierls compound CuGeO_{3} and the Haldane systems. Experimental aspects of a bond-alternating compound CuNb_{2}O_{6} are also discussed. Furthermore, the incommensurate correlation arising in this model is extensively studied, and a phase diagram is constructed.