  We present a linear response calculation for twisted bilayer graphene. The
calculation is performed for both the continuum and tight-binding models, with
the aim of assessing the validity of the former. All qualitatively important
features previously reported by us [T. Stauber et al. Phys. Rev. Lett. 120,
046801 (2018)] for the Drude matrix in the continuum model are also present in
the tight-binding calculation, with increasing quantitative agreement for
decreasing twist angle. These features include the chiral longitudinal magnetic
moment associated with plasmonic modes, and the anomalous counterflow around
the neutrality point, better interpreted as a paramagnetic response. We have
addressed the differences between Drude and equilibrium response, and shown
that orbital paramagnetism is the equilibrium response to a parallel magnetic
field over a substantial doping region around the neutrality point. Chirality
also makes the equilibrium response to exhibit a non trivial current structure
associated with the non-vertical character of interlayer bonds in the
tight-binding calculation.
