Massive Dirac quasiparticles in the optical absorbance of graphene, silicene, germanene, and tinene

Abstract

We present first-principles studies of the optical absorbance of the group IV honeycomb crystals graphene, silicene, germanene, and tinene. We account for many-body effects on the optical properties by using the non-local hybrid functional HSE06. The optical absorption peaks are blueshifted due to quasiparticle corrections, while the influence on the low-frequency absorbance remains unchanged and reduces to a universal value related to the Sommerfeld fine structure constant. At the Dirac points spin-orbit interaction opens fundamental band gaps; parabolic bands with a very small effective mass emerge. Consequently, the low-frequency absorbance is modified with a spin-orbit-induced transparency region and an increase of the absorbance at the fundamental absorption edge.

Large differences in the optical properties of a single layer of Si on Ag(110) compared to silicene

“…Similarly to the case of graphene, the absorption is equal to πα at small energies and also displays an intense feature at around 2 eV due to electronic transitions between π and π * states. This transition is located at a much smaller energy than the similar one in graphene, for which it is observed at 4.6 eV [12,14] and calculated between 4 and 5 eV [10,11,16]. This position of 2 eV is also quite below the Ag interband edge located around 3.8 eV [17], which should favor its optical observation for Si grown on Ag(110).…”

“…This has been predicted for three of them [10,11] and proved experimentally for graphene [12][13][14]. Bechstedt et al have determined the optical response of silicene by using ab initio methods based on DFT [10,15,16]. Figure 1 shows the optical absorption calculated for freestanding buckled silicene, from Ref.…”

“…Figure 1 shows the optical absorption calculated for freestanding buckled silicene, from Ref. [16]. Similarly to the case of graphene, the absorption is equal to πα at small energies and also displays an intense feature at around 2 eV due to electronic transitions between π and π * states.…”

Intrinsic Charge Transport in Stanene: Roles of Bucklings and Electron–Phonon Couplings

“…This is consistent with the trend that the value of D LA decreases with the buckling height. Namely, for graphene, silicene, germanene, and stanene, the buckling height are 0.0, 0.45, [49,61] 0.69, [8,10] and 0.85 Å, and the value of D LA are 5.0, 2.13, [29] 1.16, [30] and 0.48 eV, respectively. In addition, the elastic constants C 2D show a decreasing trend: 328.30, 85.99, [29] 55.98, [30] and 28.5 J m −1 , correspondingly.…”

“…[5] The group IV elemental analogues of graphene, including silicene, [6] germanene, [7] and stanene, [8][9][10][11] are promising alternatives going beyond graphene owing to their outstanding electronic properties. Molecular beam epitaxy technique facilitates the materials fabrications.…”