Orbital-dependent Electron-Hole Interaction in Graphene and Associated Multi-Layer Structures.
Tianqi Deng,Haibin Su +1 more
TLDR
An orbital-dependent potential is developed to describe electron-hole interaction in materials with structural 2D character, i.e. quasi-2D materials and the analysis of non-hydrogenic exciton spectrum in quasi- 2D systems clearly demonstrates the remarkable comparable contribution of orbital dependent potential with respect to non-local screening process.Abstract:
We develop an orbital-dependent potential to describe electron-hole interaction in materials with structural 2D character, i.e. quasi-2D materials. The modulated orbital-dependent potentials are also constructed with non-local screening, multi-layer screening, and finite gap due to the coupling with substrates. We apply the excitonic Hamiltonian in coordinate-space with developed effective electron-hole interacting potentials to compute excitons' binding strength at M (π band) and Γ (σ band) points in graphene and its associated multi-layer forms. The orbital-dependent potential provides a range-separated property for regulating both long- and short-range interactions. This accounts for the existence of the resonant π exciton in single- and bi-layer graphenes. The remarkable strong electron-hole interaction in σ orbitals plays a decisive role in the existence of σ exciton in graphene stack at room temperature. The interplay between gap-opening and screening from substrates shed a light on the weak dependence of σ exciton binding energy on the thickness of graphene stacks. Moreover, the analysis of non-hydrogenic exciton spectrum in quasi-2D systems clearly demonstrates the remarkable comparable contribution of orbital dependent potential with respect to non-local screening process. The understanding of orbital-dependent potential developed in this work is potentially applicable for a wide range of materials with low dimension.read more
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References
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Excitonic Effects on the Optical Response of Graphene and Bilayer Graphene
TL;DR: The resonant excitons give rise to a prominent peak in the absorption spectrum near 4.5 eV with a different line shape and significantly redshifted peak position from those of an absorption peak arising from interband transitions in an independent quasiparticle picture.
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Spectroscopic ellipsometry of graphene and an exciton-shifted van Hove peak in absorption
Vasyl G. Kravets,Alexander N. Grigorenko,Rahul R. Nair,Peter Blake,S. Anissimova,Kostya S. Novoselov,Andre K. Geim +6 more
TL;DR: In this article, the optical transparency of any two-dimensional system with a symmetric electronic spectrum is governed by the fine structure constant and suggest a simple formula that relates a quasiparticle spectrum to an optical absorption of such a system.
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Dielectric screening in two-dimensional insulators: Implications for excitonic and impurity states in graphane
TL;DR: In this article, an exact analytic form of the two-dimensional screened potential was provided for atomic thin layer insulating materials, which has strong implications for describing gap-impurity levels and also exciton binding energies.