Coulomb interaction effects on nonlinear optical response in C60, C70, and higher fullerenes
نویسنده
چکیده
Nonlinear optical properties in the fullerene C60 and the extracted higher fullerenes – C70, C76, C78, and C84 – are theoretically investigated by using the exciton formalism and the sum-overstates method. We find that off-resonant third order susceptibilities of higher fullerenes are a few times larger than those of C60. The magnitude of nonlinearity increases as the optical gap decreases in higher fullerenes. The nonlinearity is nearly proportional to the fourth power of the carbon number when the onsite Coulomb repulsion is 2t or 4t, t being the nearest neighbor hopping integral. This result, indicating important roles of Coulomb interactions, agrees with quantum chemical calculations of higher fullerenes. ∗E-mail address: [email protected]; URL: http://www.etl.go.jp/ ̃harigaya/
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