The optical absorbance of two-dimensional semiconductors is generalized to individual lattice sites through the topological marker formalism, yielding an absorbance marker. This marker allows us to investigate the atomic-scale variation of absorbance caused by impurities and thereby quantify the influence of disorder on the quantum geometry and the spread of Wannier functions of valence-band states. Applying this marker to transition-metal dichalcogenides reveals a very localized suppression of absorbance caused by potential impurities, rendering a reduction of absorbance in the macroscopic scale proportional to the impurity density, in good agreement with the experimental results of plasma-treated ${\mathrm{WS}}_2$.

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• 2-dimensional systems
• Disordered systems
• Semiconductors
• Optical spectroscopy
• Wannier function methods