Communication: Generalization of Koopmans’ theorem to optical transitions in the Hubbard model of graphene nanodots

Sheng, Weidong; Luo, Kaikai; Zhou, Aihua

doi:10.1063/1.4905789

Cited by 14 publications

(9 citation statements)

References 26 publications

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“…The e–e interactions, which were accounted through the HF approach, were emphasized to be important in determining the optical transition energies and shape of the absorption spectrum resulting in an upshift from the noninteracting spectrum by ∼0.25 eV. Specifically, the long‐range Coulomb interactions dominated in the corrections to the optical gap and exciton binding energy in graphene dots . Systematic CI calculations revealed that the e–e interaction contribution and the e–h interaction contribution are nearly cancel each other resulting in overlap of the optical and single‐particle gaps.…”

Section: Shaped Graphenementioning

confidence: 99%

“…Specifically, the long-range Coulomb interactions dominated in the corrections to the optical gap and exciton binding energy in graphene dots. [53] Systematic CI calculations revealed that the e-e interaction contribution and the e-h interaction contribution are nearly cancel each other resulting in overlap of the optical and single-particle gaps. However, the position of the exciton state is quite sensitive to a hopping parameter accounting an interaction between the nearest neighbors.…”

Section: Finite-size Configurationsmentioning

confidence: 99%

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Many‐body effects in optical response of graphene‐based structures

Bulusheva

Sedelnikova

Окотруб

2015

Int J of Quantum Chemistry

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Graphene is an exciting material for optoelectronics and plasmonics. Its optical response may be changed under mechanical action, such as stretching or corrugation, and with confinement of a size in a certain direction. Theoretical investigations play an important role in interpretation of experimental data and stimulating a search for novel graphene architectures. Thereby, it is important to analyze restrictions of modern approaches in calculation of optical properties of graphene-based objects and, particularly, to reveal an impact of electron-electron and electron-hole interactions on the position and shape of optical features. Here, we review the recent progress in quantum-chemical calculations of monolayer and few-layer graphenes, graphene ripples, and dots in a light of optical excitations.

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Section: Shaped Graphenementioning

confidence: 99%

Section: Finite-size Configurationsmentioning

confidence: 99%

Many‐body effects in optical response of graphene‐based structures

Bulusheva

Sedelnikova

Окотруб

2015

Int J of Quantum Chemistry

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“…Broken sublattice symmetry leads to formation of degenerate zero energy shells and spin polarization . Hence, controlling the size, shape, edge character, sublattice symmetry, number of layers and external screening allow for the possibility to tune electronic , optical and magnetic properties of graphene. With the realization of electronics, photonics and spintronics in a single material, graphene, one can envisage the beginning of carbononics .…”

Section: Introductionmentioning

confidence: 99%

Electronic properties and electron–electron interactions in graphene quantum dots

Özfidan

Korkusiński

Hawrylak

2015

Physica Rapid Research Ltrs

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We review the electronic properties of graphene quantum dots (GQD) with emphasis on the role of electron–electron interactions. We describe the electronic properties using a combination of tight binding, Hartree–Fock (HF), density functional theory and configuration interaction methods applied to interacting electrons on pz orbitals of carbon atoms. The electron–electron interactions are computed using Slater orbitals and screened by the environment and sigma electrons. We show that the electronic properties of graphene can be tuned by the lateral size, shape, character of edge, number of layers and screening. In particular, the energy gap can be tuned from THz to UV by varying the size of graphene quantum dot. The dependence of the gap on the size can be understood in terms of confined Dirac fermions. The effect of edges and edge reconstruction is discussed using ab‐initio techniques. The role of screening is investigated using the HF approach. HF ground states corresponding to semiconductor, Mott‐insulator, and spin‐polarized phases are obtained as a function of the strength of the screened Coulomb interactions. For GQDs in the semiconductor phase, the role of correlations in ground and excited states is computed perturbatively and shown to result in size dependent band gap renormalization. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

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“…For additional discussion of the renormalization of the absorption by e–e interactions we refer the reader to Ref. .…”

Section: Excitons In Hexagonal and Triangular Quantum Dotsmentioning

confidence: 99%

“…The ability to open up a gap in bulk graphene, a semimetal, by changing the size, shape, edge character, number of layers, carrier density and screening by the substrate offers an exciting possibility of simultaneously tuning the electronic , magnetic and, most importantly, optical properties of graphene quantum dots (GQD) continuously from THz to UV. In this contribution, we discuss the effects of electron–electron interactions on the energy gap and optical properties of graphene quantum dots.…”

Section: Introductionmentioning

confidence: 99%

Theory of optical properties of graphene quantum dots

Özfidan

Güçlü

Korkusiński

et al. 2015

Physica Rapid Research Ltrs

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We present here a theory of the optical properties of graphene quantum dots (GQDs) with tunable band gaps by lateral size confinement, from UV to THz. Starting from the Hartree-Fock ground state, we construct the correlated many-body ground and excited states of GQDs as a linear combination of a finite number of electron-hole pair excitations. We discuss the evolution of the band gap with size and its renormalization by self-energy and excitonic effects. We calculate and analyze the dipole moments of graphene quantum dots that possess a degenerate valence and conduction band edge, and construct a characteristic exciton and biexciton spectrum. We find an exciton band consisting of a pair of robust, spin singlet bright exciton states and a band of dark, spin singlet and spin triplet, exciton states at lower energies. We predict a characteristic band of biexciton levels at the band edge, discuss the Auger processes and identify a biexciton-exciton cascade. Our theoretical results are compared with experimental linear absorption and non-linear transient absorption spectra of colloidal GQDs. We next discuss the optical properties of triangular GQDs with zigzag edges whose magnetic moment can be controlled by gates. The control over the magnetic moment through carrier density manipulation results in optical spin blockade and gate tunable optical properties over a wide range of photon energies.The Science Academy, Turkey, under the BAGEP program; TUBITAK, under the BIDEP progra

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Communication: Generalization of Koopmans’ theorem to optical transitions in the Hubbard model of graphene nanodots

Cited by 14 publications

References 26 publications

Many‐body effects in optical response of graphene‐based structures

Many‐body effects in optical response of graphene‐based structures

Electronic properties and electron–electron interactions in graphene quantum dots

Theory of optical properties of graphene quantum dots

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