Spectroscopic evidence of low-energy gaps persisting up to 120 K in surface-doped p -terphenyl crystals

Using high-resolution photoemission spectroscopy on in situ potassium surface-doped para-terphenyl crystals, we uncover a low-energy spectral gap of 12 meV. This spectral gap displays a strong temperature-dependent gap-filling behavior and persists up to 120 K, which is consistent with the onset temperature of a weak steplike diamagnetic transition found in this material. Among a few potential candidates for the origin of the observed gaps, we argue that electron pairing is a plausible origin---a possibility consistent with fluctuating Cooper pairs forming near 120 K.