Microscopic Model Calculations for the Magnetization Process of Layered Triangular-Lattice Quantum Antiferromagnets

TL;DR

This study uses a numerical cluster mean-field approach to explore the magnetization process in layered triangular-lattice antiferromagnets, revealing new quantum phase transitions and aligning well with experimental data, suggesting potential for quantum simulations.

Contribution

The paper introduces a microscopic model calculation that uncovers additional quantum phase transitions in layered TLAFs and demonstrates excellent agreement with experimental results on Ba_3CoSb_2O_9.

Findings

Identification of field-induced first-order transition at H≈0.7 H_s

Discovery of multiple quantum phase transitions among coplanar phases

Excellent agreement between model calculations and experimental data

Abstract

Magnetization processes of spin-1/2 layered triangular-lattice antiferromagnets (TLAFs) under a magnetic field H are studied by means of a numerical cluster mean-field method with a scaling scheme. We find that small antiferromagnetic couplings between the layers give rise to several types of extra quantum phase transitions among different high-field coplanar phases. Especially, a field-induced first-order transition is found to occur at H\approx 0.7 H_s, where H_s is the saturation field, as another common quantum effect of ideal TLAFs in addition to the well-established one-third plateau. Our microscopic model calculation with appropriate parameters show excellent agreement with experiments on Ba_3CoSb_2O_9 [T. Susuki et al., Phys. Rev. Lett. 110, 267201 (2013)]. Given this fact, we suggest that the Co^{2+}-based compounds may allow for quantum simulations of intriguing properties of this simple frustrated model, such as quantum criticality and supersolid states.