Universal infrared absorbance of two-dimensional honeycomb group-IV crystals

Matthes, Lars; Gori, Paola; Pulci, Olivia; Bechstedt, F.

doi:10.1103/physrevb.87.035438

Cited by 168 publications

(169 citation statements)

References 45 publications

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“…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).…”

Section: Introductionmentioning

confidence: 58%

“…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.…”

Section: Introductionmentioning

confidence: 72%

“…In particular, due to the existence of the Dirac cone, the infrared absorption of these 2D layers has been shown to be equal to πα = 0.0230 at small energies, where α is the Sommerfeld fine structure constant. 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].…”

Section: Introductionmentioning

confidence: 82%

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

2014

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The optical properties of Si nanoribbons grown on Ag(110) under ultrahigh vacuum have been experimentally determined by use of in situ surface differential reflectance spectroscopy. Real-time measurements showed a clear transition of the optical response of the Si deposit at full coverage of the Ag(110) surface, corresponding to 0.8 monolayer of silicon. The spectra measured for the complete self-assembled nanoribbon layer are different from the reflectance spectrum calculated for a layer of silicene on silver, which rules out the possible silicenelike character of this layer. Furthermore, the dielectric function of the nanoribbons is calculated from the experimental data and is similar to the one of amorphous silicon, with a red shift of about 0.6 to 0.8 eV of the main absorption feature. This result indicates that the Si nanoribbons display a preferential sp 3 hybridization as in amorphous Si and not a partial sp 2 hybridization as expected for silicene.

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Section: Introductionmentioning

confidence: 58%

Section: Introductionmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 82%

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

2014

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“…Its measurement is an important tool for extracting the shape and nature of the energy bands. There are several theoretical and experimental studies on the optical conductivity in various monolayer quantum materials such as graphene [14][15][16] , silicene [17][18][19] , MoS 2 20,21 , and surface states of topological insulators [22][23][24] .…”

Section: Introductionmentioning

confidence: 99%

Effect of electron-hole asymmetry on optical conductivity in 8−Pmmn borophene

2017

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We present a detail theoretical study of the Drude weight and optical conductivity of 8-P mmn borophene having tilted anisotropic Dirac cones. We provide exact analytical expressions of xx and yy components of the Drude weight as well as maximum optical conductivity. We also obtain exact analytical expressions of the minimum energy (ǫ1) required to trigger the optical transitions and energy (ǫ2) needed to attain maximum optical conductivity. We find that the Drude weight and optical conductivity are highly anisotropic as a consequence of the tilted Dirac cone. The tilted parameter can be extracted by knowing ǫ1 and ǫ2 from optical measurements. The maximum values of the components of the optical conductivity do not depend on the carrier density and the tilted parameter. The product of the maximum values of the anisotropic conductivities has the universal value (e 2 /4 ) 2 . The tilted anisotropic Dirac cones in 8-P mmn borophene can be realized by the optical conductivity measurement.

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“…The low-energy behavior is instead dominated by the non-conical 3D Dirac cones. In contrast to the linear-energy variation of the joint density of states for Dirac cones in 2D graphene-like systems2834, in the 3D case linear bands give rise to a quadratic energy behavior of the joint density of states. Together with finite optical transition matrix elements in Table 1 and the ω −2 prefactor in expression (8) in the Methods section, finite imaginary parts arise in the limit ω → 0.…”

Section: Resultsmentioning

confidence: 90%

Electronic and optical properties of topological semimetal Cd3As2

Conte

Pulci

Bechstedt

2017

Sci Rep

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Using ab initio density functional theory the band structure and the dielectric function of a bct Cd3As2 crystal are calculated. We find a Dirac semimetal with two Dirac nodes k± near the Γ point on the tetragonal axis. The bands near the Fermi level exhibit a linear behavior. The resulting Dirac cones are anisotropic and the electron-hole symmetry is destroyed along the tetragonal axis. Along this axis the symmetry-protected band linearity only exists in a small energy interval. The Dirac cones seemingly found by ARPES in a wider energy range are interpreted in terms of pseudo-linear bands. The behavior as 3D graphene-like material is traced back to As p orbital pointing to Cd vacancies, in directions which vary throughout the unit cell. Because of the Dirac nodes the dielectric functions (imaginary part) show a plateau for vanishing frequencies whose finite value is proportional to the Sommerfeld fine structure constant but varies with the light polarization. The consequences of the anisotropy of the Dirac cones are highlighted for the polarization dependence of the infrared optical conductivity.

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Universal infrared absorbance of two-dimensional honeycomb group-IV crystals

Cited by 168 publications

References 45 publications

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

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

Effect of electron-hole asymmetry on optical conductivity in 8−Pmmn borophene

Electronic and optical properties of topological semimetal Cd3As2

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