Theory of linear optical absorption in diamond-shaped graphene quantum dots

Abstract

In this paper, optical and electronic properties of diamond shaped graphene quantum dots (DQDs) have been studied by employing large-scale electron-correlated calculations. The computations have been performed using the π-electron Pariser-Parr-Pople model Hamiltonian, which incorporates long-range Coulomb interactions. The influence of electroncorrelation effects on the ground and excited states has been included by means of the configuration-interaction approach, used at various levels. Our calculations have revealed that the absorption spectra are red-shifted with the increasing sizes of quantum dots. It has been observed that the first peak of the linear optical absorption, which represents the optical gap, is not the most intense peak. This result is in excellent agreement with the experimental data, but in stark contrast to the predictions of the tight-binding model, according to which the first peak is the most intense peak, pointing to the importance of electron-correlation effects. 1 arXiv:1501.06041v3 [cond-mat.mes-hall]

Graphene and silicene quantum dots for nanomedical diagnostics

“…51,52 It is worth noting that the anisotropic behaviour of the optical properties of QDs observed in ref. 39 and 49 disappear under the edges functionalization with OH, CH 3 and COOH. Therefore, the optical results, listed in Table 4, including absorption curves, exciton binding energy, Bohr radius and effective mass, do not depend on the light polarization direction.…”

“…Notice also that in each structure, only the hydrogen passivated to the four seam atoms, namely the atoms connecting the zigzag edges to the armchair corners, are replaced in order to obtain a signicant adjustment of the investigated property. 22,39 Hydrogen passivated C-QDs and Si-QDs, that were successfully fabricated and studied theoretically, are included for comparison. 22,[39][40][41][42] The insight into the molecular geometry of the edge-hydrogenated congurations shows that the hybridization is strongly dependent on the atom type.…”

“…22,39 Hydrogen passivated C-QDs and Si-QDs, that were successfully fabricated and studied theoretically, are included for comparison. 22,[39][40][41][42] The insight into the molecular geometry of the edge-hydrogenated congurations shows that the hybridization is strongly dependent on the atom type. More precisely, the C-C bond angles range between 118 and 123 for edgehydrogenated CQDs revealing that carbon atoms are sp 2hybridized.…”

Effects of long-range disorder and electronic interactions on the optical properties of graphene quantum dots

“…In particular, armchair and zigzag edges are the most stable edge structures [16,23,24] while GQDs with zigzag edges are found to exhibit unusual magnetic [25][26][27] and optical [28][29][30][31][32] properties due to the presence of a degenerate band of states at the Fermi level. On the other hand, armchair edges do not lead to degenerate band of states at the Fermi level, hence, can be used as small model of bulk graphene which does not have edge states [33].…”

“…Moreover, the electronic and optical properties of graphene can be manipulated at the nanoscale in a desired way by controlling lateral size, shape, type of edge, doping level and the number of layers in graphene nanostructures [11][12][13][14][15][16]. Among those various nanostructures of graphene, graphene quantum dots (GQDs) [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] offer a possibility to simultaneously control the electronic, magnetic and optical functionalities in a single material.…”