ar X iv : c on d - m at / 9 50 80 83 v 1 2 1 A ug 1 99 5 Excitons in C 60 studied by Temperature Dependent Optical Second - Harmonic Generation

Abstract

The electric dipole forbidden T1g excitonic state of solid C60 at h̄ω=1.81 eV can be probed with a Second-Harmonic Generation (SHG) experiment [1]. We show that the SHG line shape depends strongly on the degree of rotational order. We observe a splitting into two peaks below the rotational ordering phase transition temperature of 260 K. The origin of this splitting is discussed in terms of a possible Jahn-Teller effect, a possible Davydov splitting due to the four molecules per unit cell in the low temperature phase, and a mixing of the nearly degenerate T1g and Gg free molecule states because of the lower symmetry in the solid. The exciton band structure is calculated with a charge transfer mediated propagation mechanism as suggested by Lof et al. [2] and with one-electron (-hole) transfer integrals determined from band structure calculations. Comparison with our experimental SHG data leads to a reasonable agreement and shows that a mixing of T1g and Gg states may explain the splitting at low temperature. PACS numbers: 42.65.Ky, 33.70.-w, 61.46.+w. Typeset using REVTEX

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Cite this paper

@inproceedings{Sawatzky2008arXI, title={ar X iv : c on d - m at / 9 50 80 83 v 1 2 1 A ug 1 99 5 Excitons in C 60 studied by Temperature Dependent Optical Second - Harmonic Generation}, author={G. Sawatzky}, year={2008} }