PRESSURE-INDUCED SHIFT OF THE PHOTOLUMINESCENCE BAND IN SINGLE-CRYSTALS OF BUCKMINSTERFULLERENE C-60 AND ITS IMPLICATIONS FOR SUPERCONDUCTIVITY IN DOPED SAMPLES

We report the first observation of a large pressure-induced red-shift of the photoluminescence band in single crystals of C60 and the associated colour change of the sample from red to black at - 3.2 GPa. Interpreting the red shift of the luminescence band as a reduction of the bandgap E(g) of the crystal, we get the pressure derivative partial derivative E(g)/partial derivative P = -0.138 eV/GPa. This result taken in conjunction with the known compressibility, gives the deformation potential partial derivative E(g)/partial derivative (ln a) = 6.0 eV, where 'a' is the lattice constant. Taking the same value for the alkali-doped fullerene, and combining it with the known pressure dependence of the transition temperature in the context of a simple BCS expression for T(c) we estimate the electron-phonon coupling parameter lambda - 0.3.