Energy losses and transition radiation produced by the interaction of charged particles with a graphene sheet

Z. L. MISKOVIC; S. SEGUI; J. L GERVASONI; N. R. ARISTA

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Lugar: New York; Año: 2016 vol. 94 p. 1254141 - 12541417

1098-0121

We present a fully relativistic formulation of the energy loss of a charged particle traversing a conductivemonoatomic layer and apply it to the case of graphene in a Transmission Electron Microscope (TEM). Weuse two models of conductivity appropriate for different frequency regimes: (a) THz frequency range and(b) optical range. In each range we distinguish two types of contributions to the electron energy loss: theenergy deposited in graphene in the form of electronic excitations (Ohm losses), and the energy that isemitted in the form of radiation. We find strong relativistic effects in the electron energy loss spectra, whichare manifested, e.g., in the increased heights of the principal and + peaks that may be observed in TEMin the optical range. While the radiative energy losses are suppressed in the optical range in comparison tothe ohmic losses, we find that these two contributions are comparable in magnitude in the THz range, wherethe response of doped graphene is dominated by the Dirac plasmon polariton (DPP). In particular, relativecontributions of the ohmic and radiative energy losses are strongly affected by the damping of DPP. In thecase of a clean graphene with low damping, the angular distribution of the radiated spectra at the sub-THzfrequencies exhibit strong and possibly observable skewing towards graphene.