Magnetic and quantum disordered phases in triangular-lattice Heisenberg antiferromagnets

TL;DR

This paper investigates the ground-state phases of frustrated triangular-lattice Heisenberg antiferromagnets using the Schwinger-boson approach, revealing nonmagnetic quantum disordered phases and clarifying their existence and properties.

Contribution

It provides a detailed analysis of disordered phases in two specific triangular-lattice models, confirming the presence of quantum disordered states and aligning results with series expansion predictions.

Findings

Identification of nonmagnetic phases at specific parameter values.

Confirmation of quantum disordered states in the J1-J2 model.

Agreement of ground-state energy and pitch renormalization with series expansions.

Abstract

We study, within the Schwinger-boson approach, the ground-state structure of two Heisenberg antiferromagnets on the triangular lattice: the J1-J2 model, which includes a next-nearest-neighbor coupling J2, and the spatially-anisotropic J1-J'1 model, in which the nearest-neighbor coupling takes a different value J'1 along one of the bond directions. The motivations for the study of these systems range from general theoretical questions concerning frustrated quantum spin models to the concrete description of the insulating phase of some layered molecular crystals. For both models, the inclusion of one-loop corrections to saddle-point results leads to the prediction of nonmagnetic phases for particular values of the parameters J1/J2 and J'1/J1. In the case of the J1-J2 model we shed light on the existence of such disordered quantum state, a question which is controversial in the literature. For the J1-J'1 model our results for the ground-state energy, quantum renormalization of the pitch in the spiral phase, and the location of the nonmagnetic phases, nicely agree with series expansions predictions.