Cavity-enhanced circular dichroism in a van der Waals antiferromagnet

TL;DR

This paper introduces a cavity-enhanced circular dichroism method to sensitively detect magnetic order and broken symmetry in van der Waals antiferromagnets, enabling tunable and highly sensitive symmetry probing.

Contribution

It develops a novel cavity-enhanced CD technique that couples strongly with antiferromagnetic order and can be tuned via cavity parameters and material thickness.

Findings

Cavity-enhanced CD correlates with antiferromagnetic order in FePS3.

CD response can be tuned by cavity length and material thickness.

The method detects weak and hidden symmetry-breaking phenomena.

Abstract

Broken symmetry plays a pivotal role in determining the macroscopic electrical, optical, magnetic, and topological properties of materials. Circular dichroism (CD) has been widely employed to probe broken symmetry in various systems, from small molecules to bulk crystals, but designing CD responses on demand remains a challenge, especially for antiferromagnetic materials. Here, we develop a cavity-enhanced CD technique to sensitively probe the magnetic order and broken symmetry in the van der Waals antiferromagnet FePS3. By introducing interfacial inversion asymmetry in cavity-coupled FePS3 crystals, we demonstrate that the induced CD is strongly coupled with the zig-zag antiferromagnetic order of FePS3 and can be tuned both spectrally and in magnitude by varying the cavity length and FePS3 thickness. Our findings open new avenues for using cavity-modulated CD as a sensitive diagnostic probe to detect weak broken symmetries, particularly at hidden interfaces, and in systems exhibiting hidden spin polarization or strong correlations.