scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Orbital-dependent Electron-Hole Interaction in Graphene and Associated Multi-Layer Structures.

27 Nov 2015-Scientific Reports (Nature Publishing Group)-Vol. 5, Iss: 1, pp 17337-17337
TL;DR: 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.

Content maybe subject to copyright    Report

Citations
More filters
Journal ArticleDOI
TL;DR: The computed absorption spectrum unravels a remarkable absorption "gap" between the first two absorption peaks of the orthorhombic single crystal at low temperature, which points to the potential significance of defect absorption for the excellent light harvesting properties of perovskite-based solar cells.
Abstract: Electronic structure and light absorption properties of the perovskite CH3NH3PbI3 are investigated by relativistic density functional theory with quasiparticle GW corrections and many-body interactions. The nature of the Wannier exciton is studied by solving the Bethe–Salpeter equation augmented with the analysis of a conceptual hydrogen-like model. The computed absorption spectrum unravels a remarkable absorption “gap” between the first two absorption peaks. This discontinuity is maintained in the calculated tetragonal structure that, however, is not stable at low temperature. Most importantly, the discontinuity is also observed in the experimental absorption spectrum of the orthorhombic single crystal at low temperature (4 K). However, in contrast to the single crystal, in a polycrystalline perovskite film at 5 K the “gap” is filled by a monotonously increasing absorption throughout the visible range. This feature of thin films points to the potential significance of defect absorption for the excellent ...

93 citations

Journal ArticleDOI
TL;DR: In this paper, the effective nuclear charge for elements with 1 ≤ Z ≤ 118 have been performed in a Dirac-Fock approach including all relativistic effects as well as contributions from quantum electrodynamics.

21 citations

Journal ArticleDOI
TL;DR: In this article, an ab initio formalism for dipolar electron-phonon interactions (EPIs) in two-dimensional (2D) materials was developed and incorporated into Wannier-Fourier interpolation, enabling accurate EPI calculations for 2D materials and subsequent intrinsic carrier mobility prediction.
Abstract: We develop an ab initio formalism for dipolar electron-phonon interactions (EPIs) in two-dimensional (2D) materials. Unlike the purely longitudinal Fr\"ohlich model, we show that the out-of-plane dipoles also contribute to the long-wavelength nonanalytical behavior of EPIs. And the 2D dipolar EPI plays an important role not only in the typical polar material ${\text{MoS}}_{2}$, but also in graphane and fluorinated graphene. By incorporating this formalism into Wannier-Fourier interpolation, we enable accurate EPI calculations for 2D materials and subsequent intrinsic carrier mobility prediction. The results show that the Fr\"ohlich model is inadequate for 2D materials and a correct long-wavelength interaction must be included for a reliable prediction.

16 citations

Journal Article
TL;DR: The numerical results provide insight into the controversial one-dimensional hydrogen atom, which is a limiting case of the soft Coulomb problem as β → 0, using 16-digit precision calculations.
Abstract: An efficient way of evolving a solution to an ordinary differential equation is presented. A finite element method is used where we expand in a convenient local basis set of functions that enforce both function and first derivative continuity across the boundaries of each element. We also implement an adaptive step-size choice for each element that is based on a Taylor series expansion. This algorithm is used to solve for the eigenpairs corresponding to the one-dimensional soft Coulomb potential, 1/sqrt[x(2)+β(2)], which becomes numerically intractable (because of extreme stiffness) as the softening parameter (β) approaches zero. We are able to maintain near machine accuracy for β as low as β = 10(-8) using 16-digit precision calculations. Our numerical results provide insight into the controversial one-dimensional hydrogen atom, which is a limiting case of the soft Coulomb problem as β → 0.

13 citations

References
More filters
Journal ArticleDOI
TL;DR: In this paper, a theoretical analysis of the shape of the 2s2p^{1}P resonance of He observed in the inelastic scattering of electrons is presented. But the analysis is restricted to the case of one discrete level with two or more continua and of a set of discrete levels with one continuum.
Abstract: The interference of a discrete autoionized state with a continuum gives rise to characteristically asymmetric peaks in excitation spectra. The earlier qualitative interpretation of this phenomenon is extended and revised. A theoretical formula is fitted to the shape of the $2s2p^{1}P$ resonance of He observed in the inelastic scattering of electrons. The fitting determines the parameters of the $2s2p^{1}P$ resonance as follows: $E=60.1$ ev, $\ensuremath{\Gamma}\ensuremath{\sim}0.04$ ev, $f\ensuremath{\sim}2 \mathrm{to} 4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$. The theory is extended to the interaction of one discrete level with two or more continua and of a set of discrete levels with one continuum. The theory can also give the position and intensity shifts produced in a Rydberg series of discrete levels by interaction with a level of another configuration. The connection with the nuclear theory of resonance scattering is indicated.

8,210 citations

Journal ArticleDOI
30 Jan 2009-Science
TL;DR: This work illustrates the concept of graphene as a robust atomic-scale scaffold on the basis of which new two-dimensional crystals with designed electronic and other properties can be created by attaching other atoms and molecules.
Abstract: Although graphite is known as one of the most chemically inert materials, we have found that graphene, a single atomic plane of graphite, can react with atomic hydrogen, which transforms this highly conductive zero-overlap semimetal into an insulator. Transmission electron microscopy reveals that the obtained graphene derivative (graphane) is crystalline and retains the hexagonal lattice, but its period becomes markedly shorter than that of graphene. The reaction with hydrogen is reversible, so that the original metallic state, the lattice spacing, and even the quantum Hall effect can be restored by annealing. Our work illustrates the concept of graphene as a robust atomic-scale scaffold on the basis of which new two-dimensional crystals with designed electronic and other properties can be created by attaching other atoms and molecules.

3,735 citations

Book
01 Apr 1990
TL;DR: In this article, a revised second edition on the "Quantum Theory of the Optical and Electronic Properties of Semiconductors" presents the basic elements needed to understand and engage in research in semiconductor physics.
Abstract: This revised second edition on the "Quantum Theory of the Optical and Electronic Properties of Semiconductors" presents the basic elements needed to understand and engage in research in semiconductor physics. In this revised second edition misprints are corrected and some new and more detailed material is added. In order to treat the valence-band structure of semiconductors, an introduction to the k.p. theory and the related description in terms of the Luttinger Hamiltonian is included. An introductory chapter on mesoscopic semiconductor structures discussing the modifications of the envelope function approximation caused by the spatial quantum confinement is also included. Many results are developed in parallel first for bulk material, and then for quasi-two-dimensional quantum wells, and for quasi-one-dimensional quantum wires. Semiconductor quantum dots are treated in a separate chapter. The discussion of time-dependent and coherent phenomena in semiconductors has been considerably extended by including a section dealing with the theoretical description of photon echoes in semiconductors. A new chapter on magneto-absorption has been added, in which magneto-excitons and magneto-plasmas in two-dimensional systems are discussed. The chapter on electron kinetics due to the interaction with longitudinal-optical phonons has been extended. The material is presented in sufficient detail for graduate students and researchers who have a general background in quantum mechanics, and is aimed at solid state physicists, engineers, materials and optical scientists.

2,492 citations

Journal ArticleDOI
TL;DR: In this article, the selfconsistent field function for atoms with 2 to 36 electrons is computed with a minimal basis set of Slater-type orbitals, and the orbital exponent of the atomic orbitals are optimized as to ensure the energy minimum.
Abstract: The self‐consistent‐field function for atoms with 2 to 36 electrons are computed with a minimal basis set of Slater‐type orbitals. The orbital exponent of the atomic orbitals are optimized as to ensure the energy minimum. The analysis of the optimized orbital exponents allows us to obtain simple and accurate rules for the 1s, 2s, 3s, 4s, 2p, 3p, 4p, and 3d electronic screening constants. These rules are compared with those proposed by Slater and reveal the need of accounting for the screening due to the outside electrons. The analysis of the screening constants (and orbital exponents) is extended to the excited states of the groundstate configuration and to the positive ions.

2,135 citations

Journal ArticleDOI
TL;DR: It is shown that when graphene is epitaxially grown on SiC substrate, a gap of approximately 0.26 eV is produced and it is proposed that the origin of this gap is the breaking of sublattice symmetry owing to the graphene-substrate interaction.
Abstract: Graphene has shown great application potential as the hostmaterial for next-generation electronic devices. However, despite itsintriguing properties, one of the biggest hurdles for graphene to beuseful as an electronic material is the lack of an energy gap in itselectronic spectra. This, for example, prevents the use of graphene inmaking transistors. Although several proposals have been made to open agap in graphene's electronic spectra, they all require complexengineering of the graphene layer. Here, we show that when graphene isepitaxially grown on SiC substrate, a gap of ~;0.26 eV is produced. Thisgap decreases as the sample thickness increases and eventually approacheszero when the number of layers exceeds four. We propose that the originof this gap is the breaking of sublattice symmetry owing to thegraphene-substrate interaction. We believe that our results highlight apromising direction for band gap engineering of graphene.

2,132 citations