We calculate the finite-frequency conductivity of bilayer graphene with a relative twist
between the layers. The low-frequency response at zero doping shows a flat conductivity
with value twice that of the monolayer case and at higher frequency a strong absorption
peak occurs. For finite doping, the low-frequency flat absorption is modified into a peak
centered at zero frequency (the Drude response) accompanied by an interband edge which
results from the transfer of spectral weight from interband to intraband absorption due to …

We theoretically study the band structure and optical conductivity of twisted bilayer graphene
(TBG) near the magic angle considering the effects of lattice relaxation. We show that the
optical conductivity spectrum is characterized by a series of peaks associated with the van
Hove singularities in the band structure, and the peak energies evolve systematically with
the twist angle. Lattice relaxation effects in TBG modify its band structure, especially the flat
bands, which leads to significant shifts of the peaks in the optical conductivity. These results …