Measurements of the excited electron lifetime in graphite [1] with photoemission spectroscopy show that the energy dependence of the inverse lifetime is linearly proportional to the excitation energy referenced to the Fermi level. Theoretical studies [2] using a 2-dimensional Hamiltonian generalized to a system of weakly interacting layers confirm this unconventional quasiparticle lifetime in graphite.
We propose to calculate the inverse lifetime of the excited electrons in graphite using the GW approximation [3] for the imaginary part [4] of the selfenergy operator with the dielectric matrix calculated at finite frequencies within the RPA.
It seems that plasmons of very low energy -which are quickly damped down with increasing the parallel to the layers momentum- can account for the unconventional quasiparticle lifetime in graphite.
[1] S.Xu, J.Cao, C.C. Miller, D.A. Mantell. R.J.D. Miller and Y.Gao,
PRL 76 (1996) 483
[2] J. Gonzales, F. Guinea and M.A.H. Vozmediano, PRL 77 (1996) 3589
[3] M.S. Hybertsen and S.G. Louie, PRB 34 (1986) 5390
[4] P.M. Echenique, J.M. Pitarke, E.V. Chulkov and A. Rubio,
Chem Phys 251 (2000) 1
Imaginary part of the inverse dielectric function for different wave vectors q
