  This study presents the first optical spectropolarimetric study of large
C-complex asteroids. A total of 64 C-complex asteroids of different subclasses
are analyzed using archival polarimetric and reflectance data to refine the
link between polarimetric parameters and surface properties of the asteroids.
We find a consistent difference in the polarization spectra between asteroids
containing phyllosilicates and those without, which correlates with the overall
morphology of the reflectance spectrum. They exhibit broad similarities in
polarization-phase curves; nonetheless, we observe a gradual enhancement of the
negative polarization branch in the ascending order of F-B-T-Ch types, along
with an increase in reflectance curvature around 500 nm. Our observations
suggest at least for large C-complex asteroids a common mechanism underlies the
diversity in optical properties. The observed trends would be explained by the
surface composition of the asteroids, particularly optical heterogeneity caused
by carbon's varying levels of optical influence, primarily regulated by aqueous
alteration of the surfaces.
