Electron-Phonon Coupling Spectrum in Photodoped Pentacene Crystals

The coupling between conduction charges and the vibrational modes of the molecular lattic plays a defining role in the charge transport characteristics of organic semiconductors. Using electron tunneling spectroscopy, we obtain the electron-optical phonon coupling spectrum in photodoped pentacene crystals. Comparison of the tunneling spectrum to infrared absorption data on the optical phonon density-of-states yields the energy dependence of the electron-phonon scattering matrix element. The integrated spectral weight of the electron-phonon coupling shows that the superconductivity in pentacene is of electron-phonon origin.