Abstract:Various optical properties of two dimensional buckled silicene have been explored using spin unpolarized density functional theory by incorporating doping with phosphorous and aluminium atoms in the hexagonal network of pristine buckled silicene.
“…Although the structural properties of pristine silicene are well established, a comprehensive approach and description of its plasmon properties at low and high energies, from the IR to ultraviolet (UV) range, has not been presented so far. A few theoretical studies [69][70][71][72], based on the analysis of the electron energy-loss function and absorption spectrum, have reported the existence of two interband plasmons in intrinsic silicene, occurring at energies larger than 1.5 eV for vanishingly small momentum transfers. These are counterparts to the wellknown π and π-σ plasmons found in MG, BLG and graphite [73].…”
The plasmonic character of monolayer silicene is investigated by time-dependent density functional theory in the random phase approximation. Both the intrinsic (undoped) and several extrinsic (carrier doped or gated) conditions are explored by simulating injection of a probe particle (i.e., an electron or a photon) of energy below 20 eV and in-plane momentum smaller than 1.1Å 1 . The energy-loss function of the system is analyzed, with particular reference to its induced charge-density fluctuations, i.e., plasmon resonances and corresponding dispersions, occurring in the investigated energy-momentum region. At energies larger than 1.5 eV, two intrinsic interband modes are detected and characterized. The first one is a hybridized π-like plasmon, which is assisted by competing oneelectron processes involving sp 2 and sp 3 states, and depends on the slightest changes in specific geometric parameters, such as nearest-neighbor atomic distance and buckling constant. The second one is a more conventional π-σ plasmon, which is more intense than the π-like plasmon and more affected by one-electron processes involving the σ bands with respect to the analogous collective oscillation in monolayer graphene. At energies below 1 eV, two extrinsic intraband modes are predicted to occur, which are generated by distinct types of Dirac electrons (associated with different Fermi velocities at the so-called Dirac points). The most intense of them is a two-dimensional plasmon, having an energy-momentum dispersion that resembles that of a two-dimensional electron gas. The other is an acoustic plasmon that occurs for specific momentum directions and competes with the two-dimensional plasmon at mid-infrared energies. The strong anisotropic character of this mode cannot be explained in terms of the widely used Dirac-cone approximation. As in mono-, bi-, and few-layer graphene, the extrinsic oscillations of silicene are highly sensitive to the concentration of injected or ejected charge carriers. More importantly, the two-dimensional and acoustic plasmons appear to be a signature of the honeycomb lattice, independently of the chemistry of the group-IV elements and the details of the unit-cell geometry. arXiv:1610.03652v3 [cond-mat.str-el]
“…Although the structural properties of pristine silicene are well established, a comprehensive approach and description of its plasmon properties at low and high energies, from the IR to ultraviolet (UV) range, has not been presented so far. A few theoretical studies [69][70][71][72], based on the analysis of the electron energy-loss function and absorption spectrum, have reported the existence of two interband plasmons in intrinsic silicene, occurring at energies larger than 1.5 eV for vanishingly small momentum transfers. These are counterparts to the wellknown π and π-σ plasmons found in MG, BLG and graphite [73].…”
The plasmonic character of monolayer silicene is investigated by time-dependent density functional theory in the random phase approximation. Both the intrinsic (undoped) and several extrinsic (carrier doped or gated) conditions are explored by simulating injection of a probe particle (i.e., an electron or a photon) of energy below 20 eV and in-plane momentum smaller than 1.1Å 1 . The energy-loss function of the system is analyzed, with particular reference to its induced charge-density fluctuations, i.e., plasmon resonances and corresponding dispersions, occurring in the investigated energy-momentum region. At energies larger than 1.5 eV, two intrinsic interband modes are detected and characterized. The first one is a hybridized π-like plasmon, which is assisted by competing oneelectron processes involving sp 2 and sp 3 states, and depends on the slightest changes in specific geometric parameters, such as nearest-neighbor atomic distance and buckling constant. The second one is a more conventional π-σ plasmon, which is more intense than the π-like plasmon and more affected by one-electron processes involving the σ bands with respect to the analogous collective oscillation in monolayer graphene. At energies below 1 eV, two extrinsic intraband modes are predicted to occur, which are generated by distinct types of Dirac electrons (associated with different Fermi velocities at the so-called Dirac points). The most intense of them is a two-dimensional plasmon, having an energy-momentum dispersion that resembles that of a two-dimensional electron gas. The other is an acoustic plasmon that occurs for specific momentum directions and competes with the two-dimensional plasmon at mid-infrared energies. The strong anisotropic character of this mode cannot be explained in terms of the widely used Dirac-cone approximation. As in mono-, bi-, and few-layer graphene, the extrinsic oscillations of silicene are highly sensitive to the concentration of injected or ejected charge carriers. More importantly, the two-dimensional and acoustic plasmons appear to be a signature of the honeycomb lattice, independently of the chemistry of the group-IV elements and the details of the unit-cell geometry. arXiv:1610.03652v3 [cond-mat.str-el]
“…However, buckling does introduce another out-of-plane mode around 7.5 eV with strong intensity. In both indiene allotropes plasma frequencies for E||Z polarization is higher than for E||X polarization, as observed in other monolayers, like silicene 48 .Figure 4The frequency dependent energy loss spectrum, ( AB ) of buckled and planar indiene and, ( C , D ) reflectivity of buckled and planar indiene, absorption spectra, ( E , F ) of planar and buckled Indiene and, ( G , H ) optical conductivity of buckled and planar indiene. Absorbance ( I , J ) and transmittance ( K , L ) of buckled and planar indiene allotropes as the functions of energy, respectively.…”
Section: Resultsmentioning
confidence: 54%
“…Rich features in the buckled indiene (buckled silicene and borophene have only two peaks 48,49 ) come from the inter- and intra-bands transitions and plasma excitations, among other processes, contributing to the formation of EELS spectrum. Most of the peaks in the EELS are connected to the intra and inter-band excitations, while only the major peak corresponds to the energy of volume plasmons (Table 1).…”
Section: Resultsmentioning
confidence: 99%
“…Strong anisotropy is also present in the reflectivity, as the light with out-of-plane polarization will experience higher reflection at much higher energies (UV part of the spectrum), an effect seen in, for example, silicene 48 . The in-plane absorption spectrum is dominated by two groups of peaks in both indiene allotropes: the first one covers the visible (IR) frequencies range starting with very intense absorptions at 2.40 eV (1.42 eV) in the planar (buckled) allotrope; the second one appears in the UV frequency range for both allotropes.…”
In recent years, layered materials display interesting properties and the quest for new sorts of two-dimensional (2D) structures is a significance for future device manufacture. In this paper, we study electronic and optical properties of 2D indiene allotropes with planar and buckled structures. The optical properties calculations are based on density functional theory (DFT) simulations including in-plane and out-of-plane directions of light polarization. We indicate that the optical properties such as complex refractive index, absorption spectrum, electron energy loss function (EELS), reflectivity and optical conductivity spectra are strongly dependent on the direction of light’s polarization. High values and narrow peaks in optical spectra introduce indiene to the field of ultra-thin optical systems. The effect of external static electric field on electronic and optical properties of indiene is also observed and discussed. We show that the band gap in buckled indiene can be effectively changed by applying the external electric field. The discoveries here expand the group of 2D materials beyond graphene and transition metal dichalcogenides (TMDs) and give valuable data for future experimental realization of new mono-elemental materials with conceivable applications in optical devices.
“…Recently, we have demonstrated [36] the magnetism of silicene under mono-vacancy, divacancy and substituted atoms such as Al and P. The first-principles calculations indicate the highest magnetic moment for divacancy situation while zero magnetic moment for monovacancy and 2 Al doped situations. We have also studied the optical properties of silicene nanosheet with varying concentrations of Al and P [37]. It is to be noted that unlike graphene, silicene is a topological insulator which can be characterized by full insulating gap with helical gapless edges [38].…”
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