Electron-phonon and electron-electron interactions in electron doped aromatic carbon materials viewed from electrical transport*

A Mott physics on unconventional superconductors, such as cuprates, Fe pnictides, and organic conductors is now claimed for electron-doped aromatic hydrocarbon such as antracene, tetracene, pentacene, and expanded C₆₀ as well as even in graphene. Although, relatively high T_c in superconductivity was once claimed for simple aromatic hydrocarbons with electron carrier filling into their bands by alkali-metal insertion, the real electronics states have not yet been understood so far. This is partly because important scientific discussions have been made based on only limited magnetic and optical probes. The Fermi surface of A₃C₆₀ (A=alkali metals: K, Rb, Cs) superconductors with expanded cell (V_cell(C₆₀^3-)) provides an intriguing research platform for both e-e and e-ph interactions. However, being different from other unconventional superconductors, electrical transport measurements had been very difficult in expanded A₃C_60. Here, we give experimental results that accurate electrical resistivity can be achieved for a variety A₃C₆₀ with expanded V_cell(C₆₀^3-) near the Mott boundary and other hydrocarbons under various temperature (T) and pressure (P).