  We demonstrate a mechanism for magnetoresistance oscillations in insulating
states of two-dimensional (2D) materials arising from the interaction of the 2D
layer and proximal graphite gates. We study a series of devices based on
different two-dimensional systems, including mono- and bilayer Td-WTe2,
angle-aligned MoTe2/WSe2 heterobilayers and Bernal-stacked bilayer graphene,
which all share a similar graphite-gated geometry. We find that the resistivity
of the 2D system generically shows quantum oscillations as a function of
magnetic field corresponding to a high-density Fermi surface when they are
tuned near an insulating state, in contravention of na\"ive band theory.
Simultaneous measurement of the resistivity of the graphite gates show that
these oscillations are precisely correlated with quantum oscillations in the
resistivity of the graphite gates themselves. Further supporting this
connection, the oscillations are quenched when the graphite gate is replaced by
TaSe2, a high-density metal that does not show quantum oscillations. The
observed phenomenon arises from the oscillatory behavior of graphite density of
states, which modulates the device capacitance and, as a consequence, the
carrier density in the sample layer even when a constant electrochemical
potential is maintained between the sample and the gate electrode. Oscillations
are most pronounced near insulating states where the resistivity is strongly
density dependent. Our study suggests a unified mechanism for quantum
oscillations in graphite-gated 2D insulators based on sample-gate coupling.
