Plasma excitation density in a graphene-based superlattice in the presence of a strong static electric field

The density of plasma excitations in a graphene superlattice on a banded substrate in the presence of a strong static electric field is investigated. Calculations are performed on the basis of the quantum theory of plasma waves in the random phase approximation with allowance for Umklapp processes. The action of a strong electric field leads to a decrease in the frequency of plasma waves, to the appearance of collisionless damping (Landau damping) and to a shift in the peak of the density of plasma excitations toward low frequencies. Collective excitations are overlapped by single-particle excitations in the low-energy region, which will lead to a difference between theoretical and experimental data in the initial energy region.