We show that the low-frequency absorbance of undoped graphene, silicene, and germanene has a universal value, only determined by the Sommerfeld fine-structure constant. This result is derived by means of ab initio calculations of the complex dielectric function for optical interband transitions applied to two-dimensional (2D) crystals with honeycomb geometry. The assumption of chiral massless Dirac fermions is not necessary. The low-frequency absorbance does not depend on the group-IV atom, neither on the sheet buckling nor on the orbital hybridization. We explain these findings via an analytical derivation of the relationship between absorbance and fine-structure constant for 2D Bloch electrons. The effect of deviations of the electronic bands from linearity is also discussed.

Matthes, L., Gori, P., Pulci, O., & Bechstedt, F. (2013). Universal infrared absorbance of two-dimensional honeycomb group-IV crystals. PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS, 87, 035438-1-035438-9 [10.1103/PhysRevB.87.035438].

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

GORI, Paola;
2013

Abstract

We show that the low-frequency absorbance of undoped graphene, silicene, and germanene has a universal value, only determined by the Sommerfeld fine-structure constant. This result is derived by means of ab initio calculations of the complex dielectric function for optical interband transitions applied to two-dimensional (2D) crystals with honeycomb geometry. The assumption of chiral massless Dirac fermions is not necessary. The low-frequency absorbance does not depend on the group-IV atom, neither on the sheet buckling nor on the orbital hybridization. We explain these findings via an analytical derivation of the relationship between absorbance and fine-structure constant for 2D Bloch electrons. The effect of deviations of the electronic bands from linearity is also discussed.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11590/134721
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