Charge Transfer, Phase Separation, and Mott–Hubbard Transition in Potassium-Doped Coronene Films

Scanning tunneling microscopy and spectroscopy have been applied to study the pristine and potassium-doped coronene films at the molecular level with the doping ratio x ranging from 0 to 4. Both the morphology and the electronic property were found to be strongly governed by the amount of charge transfer. Certain phases of K 3 Coronene and K 4 Coronene could be fabricated at the corresponding K doping ratios. While in K 4 Coronene a doubly degenerate LUMO state of the undoped coronene became fully occupied, in K 3 Coronene that state was observed to cross the Fermi level and split into an upper unoccupied part and a lower occupied part, implying the presence of electronic correlation effect and Mott–Hubbard transition in the system. The observed four different phases of K 3 Coronene further showed different strengths of electronic correlation effect and led us to speculate that the superconductivity transition with different T c in potassium-doped coronene observed elsewhere might have an origin from the electronic correlation effect with different strengths.