Extreme Polarization of the Optical Gap and High-Energy Exciton Landscape in CrSBr
Abstract
We reveal a strongly anisotropic excitonic landscape in monolayer and bulk-like CrSBr using optical absorption spectroscopy and GW-Bethe-Salpeter equation ab initio calculations. The direct absorptive determination of the lowest bright optical onsets i.e. X0a and X0b excitons for the two in-plane polarization eigenaxes yield an in-plane optical gap anisotropy of 470 ± 15 meV. This is the highest observed value for any material in the near-infrared-to-visible spectral region to the best of our knowledge. Energetically above, we identify multiple strongly polarized excitons spanning $1.25$ eV to $3.1$ eV selectively aligned along the two orthogonal axes. A resonance X-, located $24$ meV below the X0b progressively transfers oscillator strength to Xb0, a behavior consistent with a coupled trion (Fermi-polarion)/exciton pair. Our experiments also provide polarization-resolved broadband dielectric functions of CrSBr. These results establish CrSBr as a strongly polarization-selective excitonic system and highlight its potential for polarization-selective optoelectronics enabled with its large optical-gap anisotropy.
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BibTeX
@misc{patra2026extreme,
title = {{Extreme Polarization of the Optical Gap and High-Energy Exciton Landscape in CrSBr}},
author = {Sayantan Patra and Sourabh Jain and Bhumika Chauhan and Marie-Christin Heißenbüttel and Abhisek Saidarsan and Ranjuna M. K. and Kseniia Mosina and Zdeněk Sofer and Michael Rohlfing and Thorsten Deilmann and Ashish Arora},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.29566},
eprint = {2608.29566},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.29566},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Extreme Polarization of the Optical Gap and High-Energy Exciton Landscape in CrSBr
AU - Sayantan Patra
AU - Sourabh Jain
AU - Bhumika Chauhan
AU - Marie-Christin Heißenbüttel
AU - Abhisek Saidarsan
AU - Ranjuna M. K.
AU - Kseniia Mosina
AU - Zdeněk Sofer
AU - Michael Rohlfing
AU - Thorsten Deilmann
AU - Ashish Arora
PY - 2026
DA - 2026/08/30
PB - arXiv
DO - 10.48550/arxiv.2608.29566
UR - https://arxiv.org/abs/2608.29566
AB - We reveal a strongly anisotropic excitonic landscape in monolayer and bulk-like CrSBr using optical absorption spectroscopy and GW-Bethe-Salpeter equation ab initio calculations. The direct absorptive determination of the lowest bright optical onsets i.e. X_0^a and X_0^b excitons for the two in-plane polarization eigenaxes yield an in-plane optical gap anisotropy of 470 ± 15 meV. This is the highest observed value for any material in the near-infrared-to-visible spectral region to the best of our knowledge. Energetically above, we identify multiple strongly polarized excitons spanning $1.25$ eV to $3.1$ eV selectively aligned along the two orthogonal axes. A resonance X^-, located $24$ meV below the X_0^b progressively transfers oscillator strength to X_b^0, a behavior consistent with a coupled trion (Fermi-polarion)/exciton pair. Our experiments also provide polarization-resolved broadband dielectric functions of CrSBr. These results establish CrSBr as a strongly polarization-selective excitonic system and highlight its potential for polarization-selective optoelectronics enabled with its large optical-gap anisotropy.
ER -