Band gap, excitons, and Coulomb interaction in solid<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow><mml:mrow><mml:mn>60</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Lof, R.W.; Veenendaal, M. A. van; Koopmans, B.; Jonkman, Harry T.; Sawatzky, G. A.

doi:10.1103/physrevlett.68.3924

Cited by 766 publications

(388 citation statements)

References 22 publications

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“…The effective Coulomb interaction between two electrons on a C 60 molecule in a solid is about 1-1 1 2 eV (Lof et al, 1992;Brühwiler et al, 1992;Pederson and Quong, 1992;Antropov et al, 1992). The long-ranged Coulomb interaction in the A 3 C 60 compounds leads to a charge carrier plasmon, due to the oscillations of the t 1u electrons.…”

Section: Figmentioning

confidence: 99%

“…This is a situation where we may expect particularly interesting physics, but also a situation which is particularly difficult to treat theoretically. W < U suggests very strong correlation effects (Lof et al, 1992), which have, however, not been considered in most treatment of fullerides. The similar magnitude of ω ph and W raises doubt about the strength of the retardation effects, as discussed above, and it implies that Migdal's theorem is not valid.…”

Section: Figmentioning

confidence: 99%

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Superconductivity in fullerides

1997

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Experimental studies of superconductivity properties of fullerides are briefly reviewed. Theoretical calculations of the electron-phonon coupling, in particular for the intramolecular phonons, are discussed extensively. The calculations are compared with coupling constants deduced from a number of different experimental techniques. It is discussed why the A 3 C 60 are not Mott-Hubbard insulators, in spite of the large Coulomb interaction. Estimates of the Coulomb pseudopotential µ * , describing the effect of the Coulomb repulsion on the superconductivity, as well as possible electronic mechanisms for the superconductivity are reviewed. The calculation of various properties within the Migdal-Eliashberg theory and attempts to go beyond this theory are described.

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Section: Figmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

Superconductivity in fullerides

1997

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“…The energy difference between E A and E I (the conductivity gap) is reduced by a factor of 2 when comparing the energy levels of an isolated molecule with those of a C 60 monolayer on Ag (111). Values taken from [13,21,[34][35][36][37][38][39] In the system depicted by Fig. 1c, the metal stabilizes the charged state of the C 60 -ion, since the metal effectively screens the ion.…”

Section: Introductionmentioning

confidence: 99%

“…b Energy-level diagram of the alignment of energy levels between polycrystalline Ag and bulk C 60 deduced from both UPS spectra shown in a. The HOMO-LUMO gap is taken from [37], where the energy difference is taken from the onset of the HOMO to the onset of the LUMO instead of the peak-to-peak value move downward, see Fig. 1b and c. As soon as the onset of the LUMO shifts below the Fermi level of Ag, electrons will be injected from the metal into the LUMO of the C 60 .…”

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confidence: 99%

On interface dipole layers between C 60 and Ag or Au

Veenstra

Heeres

Hadziioannou

et al. 2002

Applied Physics A: Materials Science & Processing

105

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C 60 layers on polycrystalline Ag and Au are studied by photoelectron spectroscopy. At these metal/C 60 interfaces an electron transfer occurs from the metal to the lowest unoccupied orbital of C 60 . We found in the case of the polycrystalline Ag/C 60 interface a dipolar layer with its associated electric field in the direction corresponding to the charge transfer, so pointing from the substrate to the adsorbent. Yet, at the Au/C 60 interface we observed an overall electric field pointing from C 60 towards the metal. We discuss our observations in terms of charge transfer, screening and hybridization effects and propose the occurrence of a hybridization mechanism similar to back-bonding at the Au/C 60 interface. We show that the alignment of energy levels at the metal/C 60 interface cannot simply be deduced using the metal workfunction and the frontier orbitals of C 60 , including screening effects, since hybridization effects may strongly alter the interfacial energy level structure. Our experimental findings on the polycrystalline metal/C 60 interfaces indicate an at-most weak dependence of the Fermi level of the C 60 overlayer on the workfunction of the polycrystalline metal substrate. These interfaces are found in donoracceptor-based organic photovoltaic devices and our results may help to understand the electrical characteristics of these devices.

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“…A large energy gap between succesive multiplets, and a reduced hopping rate favors insulating behavior, while the opposite happens if tunneling dominates [15].…”

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confidence: 99%

Shake-up effects and intermolecular tunneling inC60ions

1994

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The multiplet structure induced by the Coulomb interactions in C n− 60 (n = 1 − 12) is analyzed. The partially ocuppied LUMO gives rise to a set of levels which fill a relatively wide band ( ≈ 2 − 3 eV ). A large (∼ 1 eV) intramolecular effective repulsion is found. The anions are also shown to be highly polarizable. The optical absorption and photoemission spectra are calculated. The probability of exciting the molecule upon the addition or removal of one electron is shown to be significant, and this effect may give rise to the insulating behavior of K 4 C 60 . The role of intermolecular interactions in suppressing the net repulsion within the C 60 molecules is discussed. 75.10.Jm, 75.10.Lp, 75.30.Ds.

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Band gap, excitons, and Coulomb interaction in solidC60

Cited by 766 publications

References 22 publications

Superconductivity in fullerides

Superconductivity in fullerides

On interface dipole layers between C 60 and Ag or Au

Shake-up effects and intermolecular tunneling inC60ions

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