Giant Linear Dichroism Controlled by Magnetic Field in FePS$_3$

TL;DR

This paper demonstrates that magnetic fields can control giant linear dichroism in the vdW magnet FePS3, enabling tunable anisotropic optical properties through symmetry changes induced by magnetic order collapse.

Contribution

It reveals that magnetic-field-induced symmetry changes in FePS3 can control giant linear dichroism, offering a new approach for tunable magneto-optical devices.

Findings

Giant linear dichroism (~11%) observed below 120 K.

Dichroism nearly fully suppressed above 40 T.

Magnetic order collapse causes symmetry change enabling optical control.

Abstract

Magnetic-field control of fundamental optical properties is a crucial challenge in the engineering of multifunctional microdevices. Van der Waals (vdW) magnets retaining a magnetic order even in atomically thin layers, offer a promising platform for hosting exotic magneto-optical functionalities owing to their strong spin-charge coupling. Here, we demonstrate that a giant optical anisotropy can be controlled by magnetic fields in the vdW magnet FePS$_3$. The giant linear dichroism ($\sim$11%), observed below $T_{\text{N}}\!\sim\!120$ K, is nearly fully suppressed in a wide energy range from 1.6 to 2.0 eV, following the collapse of the zigzag magnetic order above 40 T. This remarkable phenomenon can be explained as a result of symmetry changes due to the spin order, enabling minority electrons of Fe$^{2+}$ to hop in a honeycomb lattice. The modification of spin-order symmetry by external fields provides a novel route for controllable anisotropic optical micro-devices.