  Most non-ferroelectric two-dimensional materials can be endowed with
so-called sliding ferroelectricity via non-equivalent homo-bilayer stacking,
which is not applicable to mono-element systems like pure graphene bilayer with
inversion symmetry at any sliding vector. Herein we show first-principles
evidence that multilayer graphene with N>3 can all be ferroelectric, where the
polarizations of polar states stem from the symmetry breaking in stacking
configurations of across-layer instead of adjacent-layer, which are
electrically switchable via interlayer sliding. The non-polar states can also
be electrically driven to polar states via sliding, all nearly degenerate in
energy, and more diverse states with distinct polarizations will emerge in more
layers. In contrast to the ferroelectric Moire domains with opposite
polarization directions in twisted bilayers reported previously, the Moire
pattern in some multilayer graphene systems (e.g., twisted monolayer-trilayer
graphene) possess nonzero net polarizations with domains of the same direction
separated by non-polar regions, which can be electrically reversed upon
interlayer sliding. The distinct Moire bands of two polar states should
facilitate electrical detection of such sliding Moire ferroelectricity during
switching.
