Excitons in two-dimensional sheets with honeycomb symmetry

Pulci, Olivia; Marsili, Margherita; Garbuio, V.; Gori, Paola; Kupchak, I. M.; Bechstedt, F.

doi:10.1002/pssb.201350404

Cited by 25 publications

(42 citation statements)

References 42 publications

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“…A quasiparticle gap at Γ of about 2.34 eV for bulk GaSe, and of 3.89 eV for a GaSe 1TL, are predicted within GW calculations [15]. The optical gaps, however, may be significantly smaller especially in the 1TL case, due to the large binding energies of the excitons in 2D systems [36,37]. This is in agreement with the value of 2.58 eV experimentally obtained from optical-absorption spectroscopy [15].…”

Section: B Electronic Structuressupporting

confidence: 85%

Lattice vibrations and electronic properties of GaSe nanosheets from first principles

Bejani

Pulci

Barvestani

et al. 2019

Phys. Rev. Materials

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Electronic properties and lattice dynamics of bulk ε-GaSe and one, two and three tetralayers GaSe are investigated by means of density functional and density functional perturbation theory. The fewtetralayers systems are semiconductors with an indirect nature of the fundamental band gap and a Mexican-hat-shape is observed at the top of the valence band. The phonon branches analysis reveals the dynamical stability for all systems considered together with the LO-TO splitting breakdown in two-dimensional systems. In-plane (E) and out-of-plane (A) zone-center lattice vibrations dominate the Raman and IR spectra. 132 132 132

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Section: B Electronic Structuressupporting

confidence: 85%

Lattice vibrations and electronic properties of GaSe nanosheets from first principles

Bejani

Pulci

Barvestani

et al. 2019

Phys. Rev. Materials

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“…The picture of the polarizability ellipsoid provides further insights into the physical nature of α 2D : r 0 is close to the exciton radius that it is confined within the 2D plane. 60 This radius is generally larger for a smaller bandgap semiconductor, and can be converted through the exciton binding energy as proposed in Refs. 29,30 r ⊥ 0 in its turn can be indirectly deduced from Stark effect for perpendicular electric fields.…”

Section: Unified Geometric Representation Of α 2dmentioning

confidence: 99%

Electronic Polarizability as the Fundamental Variable in the Dielectric Properties of Two-Dimensional Materials

et al. 2019

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The dielectric constant, which defines the polarization of the media, is a key quantity in condensed matter. It determines several electronic and optoelectronic properties important for a plethora of modern technologies from computer memory to field effect transistors and communication circuits. Moreover, the importance of the dielectric constant in describing electromagnetic interactions through screening plays a critical role in understanding fundamental molecular interactions. Here we show that despite its fundamental transcendence, the dielectric constant does not define unequivocally the dielectric properties of two-dimensional (2D) materials due to the locality of their electrostatic screening. Instead, the electronic polarizability correctly captures the dielectric nature of a 2D material which is united to other physical quantities in an atomically thin layer. We reveal a long-sought universal formalism where electronic, geometrical and dielectric properties are intrinsically correlated through the polarizability opening the door to probe quantities yet not directly measurable including the real covalent thickness of a layer. We unify the concept of dielectric properties in any material dimension finding a global dielectric anisotropy index defining their controllability through dimensionality.

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“…where the quantities U R α,β can be approximated by a model electron hole potential V (α,β) (R). The simplest model potential would be a simple screened Coulomb potential, but it has already been pointed out 6,9,10,35,[53][54][55][56] that it is not suitable for the description of anisotropically screened 2D systems. Here, we will make use of a modified Keldysh potential.…”

Section: Appendix A: Additional Computational Detailsmentioning

confidence: 99%

Excitons in few-layer hexagonal boron nitride: Davydov splitting and surface localization

et al. 2018

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Hexagonal boron nitride (hBN) has been attracting great attention because of its strong excitonic effects. Taking into account few-layer systems, we investigate theoretically the effects of the number of layers on quasiparticle energies, absorption spectra, and excitonic states, placing particular focus on the Davydov splitting of the lowest bound excitons. We describe how the inter-layer interaction as well as the variation in electronic screening as a function of layer number N affects the electronic and optical properties. Using both ab initio simulations and a tight-binding model for an effective Hamiltonian describing the excitons, we characterize in detail the symmetry of the excitonic wavefunctions and the selection rules for their coupling to incoming light. We show that for N > 2, one can distinguish between surface excitons that are mostly localized on the outer layers and inner excitons, leading to an asymmetry in the energy separation between split excitonic states. In particular, the bound surface excitons lie lower in energy than their inner counterparts. Additionally, this enables us to show how the layer thickness affects the shape of the absorption spectrum.

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Excitons in two-dimensional sheets with honeycomb symmetry

Cited by 25 publications

References 42 publications

Lattice vibrations and electronic properties of GaSe nanosheets from first principles

Lattice vibrations and electronic properties of GaSe nanosheets from first principles

Electronic Polarizability as the Fundamental Variable in the Dielectric Properties of Two-Dimensional Materials

Excitons in few-layer hexagonal boron nitride: Davydov splitting and surface localization

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