Magnon BEC and various phases of 3D quantum helimagnets under high magnetic field

TL;DR

This paper investigates the high-field phase diagram and low-energy excitations of 3D quantum helimagnets, revealing multiple magnetic phases and the potential for magnon Bose-Einstein condensation near saturation fields.

Contribution

It introduces a quantitative analysis of quantum effects in 3D helimagnets using dilute Bose gas methods, identifying three distinct phases and examining bound-magnon BEC possibilities.

Findings

Identified cone, coplanar fan, and phase-separated magnetic phases.

Mapped phase diagram of frustrated J1-J2 chains with interchain coupling.

Analyzed stability of 2-magnon bound states for bound-magnon BEC potential.

Abstract

We study high-field phase diagram and low-energy excitations of three-dimensional quantum helimagnets. Slightly below the saturation field, the emergence of magnetic order may be viewed as Bose-Einstein condensation (BEC) of magnons. The method of dilute Bose gas enables a quantitative analysis of quantum effects in these helimagnets and thereby three phases are found: cone, coplanar fan and a phase-separated one. As an application, we map out the phase diagram of a 3D helimagnet which consists of frustrated J1-J2 chains as a function of frustration and an interchain coupling. Moreover, we also calculate the stability of the 2-magnon bound state to investigate the possibility of the bound-magnon BEC.