engleski

Spectral properties of Dirac electron system

Dirac electrons have been applied in condensed matter physics to study a variety of novel materials, including graphene and recently discovered three-dimensional topologycal insulators. Other recent examples of Dirac electron systems include monolayer of molybdenum disulfide (ML-MDS) and sillicene. Comparing with graphene, the biggest difference in three-dimensional toplogycal insulators, monolayer MoS2 and sillicene are gapped Dirac electrons found in these materials. Two-dimensional Dirac electron systems have been investigated by angle resolved photoemission spectroscopy (ARPES) measurements that provide direct probe of the electronic structure and the electron self-energy which takes into account electronic correlations and comprises collective modes. The early G0W0 approach to the three-dimensional , , jellium'' model resulted in the spectral function showing low energy quasi-particle peaks and additional features due to the plasmon mode. Analog results were reported for graphene. Also, our earlier G0W0 approach to spectral properties of quasi-one-dimensional conductors introduced wide features into the spectral function originating from the anisotropic plasmon dispersion due to the finite electron-electron Coulomb interaction. We present the extension of our previous G0W0 approach to the two-dimensional system of massless Dirac electrons interacting via the long-range Coulomb interaction. We determine the one-particle spectral function taking into account only a partially filled linear band above the Dirac point. The electron self-energy is calculated, paying particular attention to the contribution coming from the collective plasmon mode. The obtained results show a dispersing feature in the spectral function and a low energy quasi-particle with the renormalized free-electron spectral weight. We expect the results obtained to be qualitatively in agreement with spectral properties of monolayer of MoS2 which has the large direct band gap between the valence and conduction bands. Our findings may also set an insight on spectral properties of recently fabricated two-dimensional semiconductor phosphorene which unlike monolayer of MoS2 exhibits an anisotropic band dispersion around the large direct band gap. We also discuss the influence of the underlying substrate on the obtained results.

Plasmon; Spectral function

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