Quantum Phase Transitions in Two-Dimensional Spin Systems with Ladder, Plaquette and Mixed-Spin Structures

TL;DR

This paper investigates quantum phase transitions in 2D antiferromagnetic spin systems with various structures, using series expansion and approximants to map phase boundaries, aligning well with prior quantum Monte Carlo findings.

Contribution

It introduces a series expansion method combined with Dlog and biased Padé approximants to analyze phase boundaries in complex 2D spin systems, providing a quantitative phase diagram.

Findings

Phase boundaries are accurately determined for different structures.

Results agree with previous quantum Monte Carlo studies.

Method effectively captures quantum phase transitions.

Abstract

Quantum phase transitions between the magnetically ordered and disordered states are studied for the two-dimensional antiferromagnetic quantum spin systems with ladder, plaquette, and mixed-spin structures. Starting with properly chosen singlet-cluster configurations, we perform the series expansion for the staggered magnetic susceptibility. The phase boundary is determined by applying the Dlog and biased Pad\'e approximants to the staggered susceptibility thus obtained. The resulting phase diagram allows us to discuss the quantum phase transitions quantitatively, which agrees fairly well with the quantum Monte Carlo results for several cases previously studied.