Ground State Property of an Alternating Spin Ladder Involving Two Kinds of Inter-Chain Interactions

TL;DR

This study investigates the ground state phases of an alternating spin ladder with two types of inter-chain interactions, revealing phase transitions and stability conditions using exact diagonalization.

Contribution

It introduces a detailed phase diagram for an alternating spin ladder with competing inter-chain interactions, highlighting the stability of ferrimagnetic and singlet phases.

Findings

Ferrimagnetic ground state becomes unstable with small inter-chain interactions.

The phase diagram shows regions of ferrimagnetic and singlet ground states.

The phase transition nature depends on the ratio of inter-chain interactions.

Abstract

The ground state property of the alternating spin ladder is studied in the case that the system involves an antiferromagnetic intra-chain interaction as well as two kinds of inter-chain interactions; one is between spins of the same magnitude and the other is between spins with different magnitudes. The calculation has been carried out by the exact diagonalization method. As a consequence of the competition among interactions, the system is revealed to show an interesting variety of phases in the ground state property. Its phase diagram is exhibited in the parameter space of the system. We find that, however small the total amount of the inter-chain interactions is, the ferrimagnetic ground state becomes unstable in a certain region. In this case, which of the ferrimagnetic and the singlet ground state to appear is determined only by the ratio between the inter-chain interactions regardless of their total amount. The nature of two phases appearing in the singlet region of the phase diagram and the type of the phase transition between them are also discussed. The results are ensured by comparing with those of obtained in other models which are contained in our model as special limiting cases.