A Theoretical Study Showing K2picene as a Parent Semiconductor for Organic Superconductivity

Abstract

Based on the density functional theory (DFT), a theoretical determination method is applied to find structural and electronic properties of potassium-doped picene. In a unit cell of K 2 picene observed experimentally, the atomic positions and the electronic state are determined within a generalized-gradient approximation of DFT using the plane-wave expansion method. Some metastable structures of K 2 picene are found in the optimization simulations. Notable properties of a structure with AB stacking, which is the lowest in the energy than others, are 1) appearance of electron doped molecular bands with the band width of 0.1–0.4 eV, 2) gap formation with a gap of 0.04–0.1 eV at the Fermi energy, and 3) narrow conduction bands with the band width of ∼0.1 eV. In all meta-stable structures determined in this study, these characteristics are commonly found. Assuming further electron doping in the conduction bands of K 2 picene, electron–correlation effects may appear as the pair-hopping processes between doped ...