1995/08/21 by A. M. Janner, A. Janner, R. Eder +4 · 1 citation
Chemistry · Materials Science · Physics and Astronomy · #Advanced Chemical Physics Studies #Fullerene Chemistry and Applications #Graphene research and applications #cond-mat
paper · pdf · doi:10.1103/physrevb.52.17158
Revtex-file, 18 pages + 6 figures appended as uu-encoded postscript
arxiv created 1995/08/21 · openalex publication_date 1995/12/15 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
The electric-dipole-forbidden 1T1g excitonic state of solid C60 at \ensuremath\Elzxh\ensuremathω=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 suggested by Lof et al. 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 1\mathrm\ensuremathΓ1g and 1Gg states may explain the splitting at low temperature.