Two-Dimensional Quantum Spin Systems with Ladder and Plaquette Structure

TL;DR

This paper studies two-dimensional quantum spin systems with ladder and plaquette structures, analyzing their low-energy properties, phase transitions, and the effects of bond and spin alternations using advanced theoretical models.

Contribution

It introduces a combined non-linear sigma model and spin wave approach to evaluate spin gaps and magnetization in complex 2D quantum spin systems with novel structural features.

Findings

Identification of spin gaps and magnetization behavior

Description of quantum phase transition between ordered and disordered states

Insights into how spin-gapped phases evolve into antiferromagnetic phases

Abstract

We investigate low-energy properties of two-dimensional quantum spin systems with the ladder and plaquette structures, which are described by a generalized antiferromagnetic Heisenberg model with both of the bond and spin alternations. By exploiting a non-linear $\sigma$ model technique and a modified spin wave approach, we evaluate the spin gap and the spontaneous magnetization to discuss the quantum phase transition between the ordered and disordered states. We argue how the spin-gapped phase is driven to the antiferromagnetic phase in the phase diagram.