Collective excitations in spin-polarized bilayer graphene

Abstract

We calculate the plasmon frequency and damping rate of plasma oscillations in a spin-polarized BLG system. Using the long wavelength approximation for dynamical dielectric function, we obtain an analytical expression for plasmon frequency showing that the degree of spin polarization P has negligible effect on the long wavelength plasmon frequency. Numerical calculations demonstrate that the degree of spin polarization affects slightly (strongly) plasmon frequency at small (large) wave-vectors and the maximum value of damping rate increases with increasing P. We also study the effects of carrier density and substrate dielectric constant on plasmon properties for different value of spin polarization. The numerically calculated critical wave-vector, at which the plasmon dispersion curve hits the edge of electron-hole continuum, decreases with P and can be used to determine experimentally the degree of spin polarization.