  Ordered mesoscale structures in 2D materials induced by small misorientations
have opened pathways for a wide variety of novel electronic, ferroelectric, and
quantum phenomena. Until now, the only mechanism to induce this periodic
ordering was via mechanical rotations between the layers, with the periodicity
of the resulting moir\'e pattern being directly related to twist angle. Here we
report a fundamentally new mechanism for emergence of mesoscopic periodic
patterns in multilayer sulfur-containing metal phosphorous trichalcogenide,
MnPS$_{3}$, induced by the electron beam. The formation under the beam of
periodic hexagonal patterns with several characteristic length scales,
nucleation and transitions between the phases, and local dynamics are
demonstrated. The associated mechanisms are attributed to the relative
contraction of the layers caused by beam-induced sulphur vacancy formation with
subsequent ordering and lattice parameter change. As a result, the plasmonic
response of the system is locally altered, suggesting an element of control
over plasmon resonances by electron beam patterning. We pose that harnessing
this phenomenon provides both insight into fundamental physics of quantum
materials and opens a pathway towards device applications by enabling
controlled periodic potentials on the atomic scale.
