Interplay of vibrational, electronic, and magnetic states in CrSBr

Abstract The van der Waals antiferromagnet CrSBr exhibits coupling of vibrational, electronic, and magnetic degrees of freedom, giving rise to distinctive quasi-particle interactions. We investigate these interactions across a wide temperature range using polarization-resolved Raman spectroscopy at various excitation energies, complemented by optical absorption and photoluminescence excitation (PLE) spectroscopy. Under 1.96 eV excitation, we observe pronounced changes in the $${A}_{g}^{1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mstyle> <mml:mi>A</mml:mi> </mml:mstyle> </mml:mrow> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , $${A}_{g}^{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mstyle> <mml:mi>A</mml:mi> </mml:mstyle> </mml:mrow> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , and $${A}_{g}^{3}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mstyle> <mml:mi>A</mml:mi> </mml:mstyle> </mml:mrow> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> Raman modes near the Néel temperature, coinciding with modifications in the oscillator strength of excitonic transitions and clear resonances in PLE. The distinct temperature evolution of Raman tensor elements and polarization anisotropy of Raman modes indicates that they couple to different excitonic and electronic states. The suppression of the excitonic states' oscillation strength above the Néel temperature could be related to the magnetic phase transition, thereby connecting these excitonic states and Raman modes to a specific spin alignment. We develop a simple model that describes how magnetic order impacts excitonic states and hence the intensity and polarization of the Raman scattering signal. These observations make CrSBr a versatile platform for probing quasi-particle interactions in low-dimensional magnets and provide insights for applications in quantum sensing and quantum communication.