Encapsulated low-energy graphene plasmons under strain and the effect of plasmon-phonon coupling

The combined effect due to strain, encapsulation and phonon scattering on the plasmon excitation
spectrum of a graphene layer is investigated. The calculations are based on the random-phase
approximation (RPA) for the surface response function which yields the plasmon dispersion equation
that is applicable in the presence or absence of an applied uniaxial strain. We present results showing
the dependence of the frequency of the charge density oscillations on the strain modulus and direction
of the wave vector in the Brillouin zone.