Raman Polarization Switching in CrSBr

TL;DR

This study investigates the polarization-dependent Raman scattering in CrSBr, revealing complex electron-phonon interactions and polarization rotation of specific vibrational modes related to its anisotropic magnetic and electronic properties.

Contribution

It provides new insights into the polarization behavior of Raman modes in CrSBr and uncovers resonant electron-phonon coupling effects linked to its anisotropic structure.

Findings

Polarization of A$_g^2$ mode can rotate by 90 degrees depending on excitation energy.

A$_g^1$ and A$_g^3$ modes remain polarized along the b axis regardless of laser energy.

Resonant electron-phonon coupling is observed through analysis of Raman tensor components.

Abstract

Semiconducting CrSBr is a layered A-type antiferromagnet, with individual layers antiferromagnetically coupled along the stacking direction. Due to its unique orthorhombic crystal structure, CrSBr exhibits highly anisotropic mechanical and optoelectronic properties acting itself as a quasi-1D material. CrSBr demonstrates complex coupling phenomena involving phonons, excitons, magnons, and polaritons. Here we show through polarization-resolved resonant Raman scattering the intricate interaction between the vibrational and electronic properties of CrSBr. For samples spanning from few-layer to bulk thickness, we observe that the polarization of the A$_g^2$ Raman mode can be rotated by 90 degrees, shifting from alignment with the crystallographic a (intermediate magnetic) axis to the b (easy magnetic) axis, depending on the excitation energy. In contrast, the A$_g^1$ and A$_g^3$ modes consistently remain polarized along the b axis, regardless of the laser energy used. We access real and imaginary parts of the Raman tensor in our analysis, uncovering resonant electron-phonon coupling.