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We present an experimental and systematic theoretical study of the optical proper- ties of anisotropic excitons in GeS encapsulated in hexagonal BN with the aid of a com- prehensive approach that combines polarization-resolved and temperature-dependent photoluminescence (PL) measurements, ab initio calculations, and effective mass ap- proximation (EMA). Our results demonstrate that the Coulomb interaction included by the Bethe-Salpeter Equation (BSE) method significantly impacts and modifies the optical absorption spectra in GeS, highlighting the crucial role of excitonic effects on optical properties. Moreover, we show that the imaginary part of the dielectric function exhibits a significant dependence on the direction of polarization. By combining ab initio calculations with the EMA, we are able to study the quasi-hydrogenic exciton states, oscillator strength, and PL spectroscopy of GeS along both the zigzag and armchair axes. We demonstrate that, unlike the isotropic hydrogenic model, the perturbation induced by anisotropy reduces the symmetry of the system, resulting in the lift of degeneracy and a mixture of exciton states. Our theoretical modeling demon- strates a strong correlation with our experimental results, providing validation of our approach.

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• https://creativecommons.org/licenses/by/3.0/legalcode
  

Keyword: Anisotropic excitons, GeS, optical properties

Date published: 2023-10-16

Publisher: Royal Society of Chemistry (RSC)

Journal:

• Nanoscale (ISSN: 20403372) vol. 15 issue. 42 p. 17014-17028

Funding:

• Narodowym Centrum Nauki 2017/27/B/ST3/00205
• Narodowym Centrum Nauki 2018/31/B/ST3/02111
• Ministry of Education - Singapore C-33-18-279-V12
• Ministry of Education - Singapore MOE-T2EP50122-0012
• Air Force Office of Scientific Research FA8655-21-1-7026
• Japan Society for the Promotion of Science 20H00354
• Japan Society for the Promotion of Science 23H02052
• Ministry of Education, Culture, Sports, Science and Technology

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1039/d3nr03168c

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Updated at: 2025-02-15 12:30:30 +0900

Published on MDR: 2025-02-15 12:30:30 +0900