We have experimentally revealed the band structure and the surface Brillouin zone of insulating picene single crystals (SCs), the mother organic system for a recently discovered aromatic superconductor, with ultraviolet photoelectron spectroscopy (UPS) and low-energy electron diffraction with a laser for photoconduction. A hole effective mass of $2.24m_0$ and the hole mobility ${\mu }_h\ge 9.0{\mathrm{cm}}^2/\mathrm{V}\mathrm{s}$ (298 K) were deduced in the $\Gamma \mathrm{\text{−}}Y$ direction. We have further shown that some picene SCs did not show charging during UPS even without the laser, which indicates that pristine UPS works for high-quality organic SCs.

• Received 4 January 2012

DOI:https://doi.org/10.1103/PhysRevLett.108.226401