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<p>Reflection anisotropy spectroscopy is widely used to probe the optical properties of surfaces, yet the origin of the ’bulk-related’ features has been debated for decades. It is often argued that these features are related to surface-induced bulk anisotropy because they coincide with critical energies of the bulk dielectric function. Here, we show that a quantitative understanding of these features requires an explicit analysis of excitonic contributions. We introduce a layer-resolved exciton localization measure within the framework of many-body perturbation theory, enabling a direct assessment of the spatial origin of optical anisotropies. Applying this approach to arsenic-modified silicon reconstructions, we find that, depending on the surface structure, the apparent ’bulk-related’ features originate predominantly from surface-localized states. Supported by low-temperature reflection anisotropy measurements, our findings challenge the traditional explanation of surface-induced bulk anisotropy and suggest that bulk-enhanced surface anisotropies also contribute to, or are responsible for, these features.</p>

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On the origin of bulk-related anisotropies in surface optical spectra

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2026年2月26日

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  • Max Großmann,
  • Kai Daniel Hanke,
  • Chris Yannic Bohlemann,
  • Agnieszka Paszuk,
  • Thomas Hannappel,
  • Wolf Gero Schmidt,
  • Erich Runge

摘要

Reflection anisotropy spectroscopy is widely used to probe the optical properties of surfaces, yet the origin of the ’bulk-related’ features has been debated for decades. It is often argued that these features are related to surface-induced bulk anisotropy because they coincide with critical energies of the bulk dielectric function. Here, we show that a quantitative understanding of these features requires an explicit analysis of excitonic contributions. We introduce a layer-resolved exciton localization measure within the framework of many-body perturbation theory, enabling a direct assessment of the spatial origin of optical anisotropies. Applying this approach to arsenic-modified silicon reconstructions, we find that, depending on the surface structure, the apparent ’bulk-related’ features originate predominantly from surface-localized states. Supported by low-temperature reflection anisotropy measurements, our findings challenge the traditional explanation of surface-induced bulk anisotropy and suggest that bulk-enhanced surface anisotropies also contribute to, or are responsible for, these features.