  Nonreciprocal plasmonics enables one-way light propagation at the nanoscale
and it is an essential building block for photonics applications. Here, we
explore intrinsic nonreciprocity in bulk plasmon propagation based on
underlying symmetries. We demonstrate that the interband, as well as the
intraband bulk plasmon modes, follow asymmetric dispersion depending on the
sign of the wavevector for systems with broken inversion and time-reversal
symmetry. We show that the nonreciprocity in the interband plasmon dispersion
is dictated by the quantum metric connection, which is a band geometric
quantity. The intrinsic nonreciprocity in bulk intraband plasmon dispersion is
dictated by the quantum metric dipole and a higher-order `Drude' weight-like
term. We corroborate our findings via explicit numerical calculations for the
two-dimensional Qi-Wu-Zhang model and demonstrate the existence of intrinsic
nonreciprocal intraband and interband plasmon modes in moire systems such as
twisted bilayer graphene.
