Optical properties of two-dimensional honeycomb crystals graphene, silicene, germanene, and tinene from first principles

Abstract

We compute the optical conductivity of 2D honeycomb crystals beyond the usual Dirac-cone approximation. The calculations are mainly based on the independent-quasiparticle approximation of the complex dielectric function for optical interband transitions. The full band structures are taken into account. In the case of silicene, the influence of excitonic effects is also studied. Special care is taken to derive converged spectra with respect to the number of k points in the Brillouin zone and the number of bands. In this way both the real and imaginary parts of the optical conductivity are correctly described for small and large frequencies. The results are applied to predict the optical properties reflection, transmission and absorption in a wide range of photon energies. They are discussed in the light of the available experimental data.

Continuous Germanene Layer on Al(111)

“…The structure of the latter consists of a Ge honeycomb network in which half of the germanium atoms have higher positions than the other half (bilayer model). 33,[36][37][38][39][40][41][42][43][44][45] The Ge-Ge nearest neighbors distances in freestanding germanene are found to be d Ge−Ge to the normal to the sample surface and is varied from 0˚up to 80˚. Also shown in Figure 10 Page 10 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 …”

“…These observations seem to exclude the formation of a metastable, or unstable, Al-Ge alloy, whose stability would be only achieved in such a narrow temperature range.The experimental observations given by STM have been the starting point of the DFT study presented below. Theoretical models can be found in the literature on Ag(111) andAl(111), invoking Ge adatoms, Ge atoms shifted upwards or downwards 31,33,[36][37][38][40][41][42][43][44][45]. The model used for the present calculations involves one Ge monolayer, with part of the Ge atoms placed in a honeycomb network, as suggested by STM measurements.…”

How to Make Devices with Weyl Materials

“…The similarities between T weyl and T optics are most obvious when considering that both systems experience resonance under the condition dq = nπ . The resonance condition for the three-dimensional Weyl fermions expands to (27) and in the optical case…”

Infrared to ultraviolet optical response for armchair-edge silicene nanoribbons

“…In recent years, many fascinating properties for two-dimensional honeycomb structural materials [1][2][3][4][5][6][7][8][9][10][11][12][13] have been investigated. The electronic structure and optical properties for germanene/tinene, [3] phosphorene [4,5], and molybdenum disulfide [6,7] have been demonstrated, while the nanoscale silicene [8][9][10][11][12][13] should be more interesting and significant in future nanoelectronic devices.…”

“…The electronic structure and optical properties for germanene/tinene, [3] phosphorene [4,5], and molybdenum disulfide [6,7] have been demonstrated, while the nanoscale silicene [8][9][10][11][12][13] should be more interesting and significant in future nanoelectronic devices.…”