  The physics of flat band is novel and rich but difficult to access. In this
regard, recently twisting of bilayer van der Waals (vdW)-bounded
two-dimensional (2D) materials has attracted much attention, because the
reduction of Brillouin zone will eventually lead to a diminishing kinetic
energy. Alternatively, one may start with a 2D Kagome lattice, which already
possesses flat bands at the Fermi level, but unfortunately these bands connect
quadratically to other (dispersive) bands, leading to undesirable effects.
Here, we propose, by first-principles calculation and tight-binding modeling,
that the same bilayer twisting approach can be used to isolate the Kagome flat
bands. As the starting kinetic energy is already vanishingly small, the
interlayer vdW potential is always sufficiently large irrespective of the
twisting angle. As such the electronic states in the (connected) flat bands
become unstable against a spontaneous Wigner crystallization, which is expected
to have interesting interplays with other flat-band phenomena such as novel
superconductivity and anomalous quantum Hall effect.
