Electron-hole interaction

Brus L E 1984 Electron-electron and electron-hole Interactions In small semiconductor crystallites the size dependence of the lowest excited electronic state J. Chem. Phys. 80 4403-9... 

Brus, L. E. (1984). Electron-electron and Electron-Hole Interactions in Small Semiconductor... 

If we neglect the electron-hole interaction, as in Chapter 1, then a metal-insulator transition should occur when the two bands overlap. For infinite values of a, the separation in energy between the two bands should be just the Hubbard Uy so the transition occurs when... 

The presence in the cluster of a positively charged impurity has also been considered, analyzing, by first principles, the screening due to the Si-NCs [123,124]. A reduction of screening in Si nanostructures with respect to bulk Si has been already observed [52] and predicted [125]. This reduction is a fundamental process at the basis of the enhancement of both the electron-hole interaction and the impurity activation energies in nanosized objects, and is due to the fact that close to the surface there is a dielectric dead layer, with a finite-range reduction of the dielectric constant due to the dielectric mismatch at the nanocrystal-environment interface. 

In particular we will show the dependence of the electronic gap on both wire size and orientation. Further, in some of the studied wires, self-energy corrections, by means of the GW method, and also electron-hole interaction, by solving the Bethe-Salpeter equation, will be included in order to have an appropriate description of the excited states. 

Excitation of the polymer creates one electron and a hole on the chain. This effect is particularly important when the electron-hole interactions are strong. Coulomb attraction keeps them together and we consider the two opposite charges as a bound electron-hole pair. An exciton (Fig. 1.11) is named according to its delocalisation. If it is localised, it is called a Frenkel exciton and, if it is delocalised, i.e., it extends over many molecular units, it is a Mott-Wannier type of exciton. ... 

Interestingly also the electron-hole interaction can scale with such a distance law. The pre-melting corresponds then to what is called level narrowing,90 and the transition to a superionic state (degenerate situation) corresponds to the insulator-metal transition expected in such a case. 

Charge transfer excitations simulated by quasi-particle techniques lack the electron-hole interaction (excitonic effect) because the two excess charges... 

The net charge distribution p(x, x) = ne (x, x) — n, i(x, x) can 0e used for computing the energy functional of the electron-electron and electron-hole interactions in the tunnel gap. The potential energy of the induced charges as a function of the dot location is proportional to the integral... 

With the electron and hole confined to the QD core, strong electron-hole interaction leads to efficient, fast relaxation via the Auger mechanism, and in QDs where the hole is localised at the surface, the increased spatial separation inhibits the Anger process and results in slower relaxation. The data imply that hole trapping at the intrinsic surface state occurs in less than 75 fs (Blackburn et al, 2003). 

Klimov V. I., Mikhailovsky A. A., McBranch D. W., Leatherdale C. A. and Bawendi M. G. (2000), Mechanisms for intraband energy relaxation in semicondnctor quantum dots the role of electron-hole interactions , Phys. Rev. B 61, R13349-R13352. 

We have seen that the inner hole can produce a perturbation of the electronic distribution relatively to that of the unperturbed solid. Various analyses have shown the importance of the final-state configuration on the spectra and the electron-hole interactions which can, in some cases, alter their shape. Thus, the rare earth 3 d photoabsorption spectra present a number of structures which spread over several eV. They can be interpreted as the components of multiplets because of the exchange coupling between the 3 d and 4/shells. The perturbation weakens as the hole lies in a deeper inner shell. In fact, the exchange interaction strength depends on the overlap between the wavefunctions of the inner hole and the localized 4/holes the weaker... 

The zero value of the energy (1.5) coincides with the bottom of the conduction band and its absolute value for k = 0 is equal to the binding energy of the electron and the hole in the exciton. The relatively simple relation between the Wannier-Mott exciton energy does not hold when the electron-hole interaction is treated more accurately (see (8)), and becomes a relation of a more general type. 

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