Magnon gap excitations and spin-entangled optical transition in van der Waals antiferromagnet NiPS3

TL;DR

This study uses optical magneto-spectroscopy to explore magnon gaps and spin-entangled excitations in NiPS3, revealing split magnon modes and magnetic field effects on optical excitations, advancing understanding of its magnetic and optical properties.

Contribution

It provides new insights into the magnon gap splitting and the nature of optical excitations in NiPS3, proposing models for their behavior under magnetic fields.

Findings

Magnon gap splits into two components, indicating biaxial magnetic character.

Near-infrared photoluminescence shows excitation splitting under magnetic field.

Correlations established between optical excitations and magnon properties.

Abstract

Optical magneto-spectroscopy methods (Raman scattering, far-infrared transmission, and photoluminescence) have been applied to investigate the properties of the NiPS3 semiconducting antiferromagnet. The fundamental magnon gap excitation in this van der Waals material has been found to be split into two components, in support of the biaxial character of the NiPS3 antiferromagnet. Photoluminescence measurements in the near-infrared spectral range show that the intriguing 1.475 eV-excitation unique to the NiPS3 antiferromagnetic phase splits upon the application of the in-plane magnetic field. The observed splitting patterns are correlated with properties of magnon excitations and reproduced with the simple model proposed. Possible routes toward a firm identification of the spin-entangled 1.475 eV-optical excitation in NiPS3, which can hardly be recognized as a coherent Zhang-Rice exciton, are discussed.