| Excitons in C60 studied by temperature-dependent optical second-harmonic generation (1995) | |||||||||||||
Abstract | |||||||||||||
| The electric-dipole-forbidden 1T1g excitonic state of solid C60 at ħω=1.81 eV can be probed with a second-harmonic generation (SHG) experiment. 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 1T1g and 1Gg 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 earlier suggested 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 1T1g and 1Gg states may explain the splitting at low temperature. | |||||||||||||
Publication details | |||||||||||||
| |||||||||||||