engleski

Electronic excitations in Dirac/Weyl semimetals

Three-dimensional topological Dirac/Weyl semimetals, which can be seen as the three- dimensional analogs of graphene, have been intensively studied recently. We apply the dielectric formalism within the random phase approximation (RPA) and G0W0 approximation to the three-dimensional topological Dirac/Weyl semimetals with the Coulomb electron-electron interaction in order to calculate the one- particle spectral function for conducting electron band and investigate the surface excitation spectrum. The RPA dielectric response comprises a bulk plasmon mode which is responsible for the appearance of a dispersing feature in the spectral function and the renormalization of the free-electron spectral weight. Also, it leads to the appearance of a well-defined surface plasmon mode in the structure factor, which gives the surface excitation spectrum for the semi-infinite semimetal, due to the plasmon mode in the bulk. Namely, the surface dielectric function, which determines the structure factor, comprises the RPA bulk dielectric function within presented formalism. The obtained surface plasmon dispersion always stays below the bulk plasmon dispersion. Moreover, it is shown that the influence of the electron-hole excitations on the surface excitation spectrum is important at large surface wave vectors. Our findings set a new insight on the role of plasmon mode in the spectral properties of the three- dimensional topological Dirac/Weyl semimetals. The obtained results are useful for experiments by angle- resolved photoemission spectroscopy (ARPES) and momentum-resolved low energy electron energy-loss spectroscopy (EELS) in these materials.

Dirac/Weyl semimetals ; plasmon ; surface plasmon

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