Twisted multilayer graphene exhibiting strong absorption bands induced by van Hove Singularities

摘要

Twisted bilayer graphene exhibits several angle-dependent properties due to the emergence of the van Hove Singularities in its density of states. Among them, twist-angle-dependent optical absorption has gained a lot of attention due to its presence in the visible spectral region. However, observation of such absorption is experimentally tricky due to large transmittance. In this study, we use highly decoupled twisted multilayer graphene to observe such absorption in thevisible region using a simple spectrometer. A large number of twisted graphene layers in the system enable observation of such absorption evident in the visible region; the absorption band position correlates with the twist angle measuredusing selective area electron diffraction pattern as well as predictions from theory. While the Raman spectra were akin to those of the decoupled graphene system, at specific twist angle of $sim$13$^{circ}$, the spectrum contained clear signatures of G-band enhancement.