Superconductivity and phase stability of potassium-doped p-quinquephenyl

The chain-like organic compounds with conjugated structure have the potential to become high temperature superconductors. Here, we show that p-quinquephenyl containing five phenyl rings connected in para position is superconducting when the compound is doped by potassium, with a critical temperature of 7.3K. The dc magnetic susceptibility measurements provide solid evidence for the presence of Meissner effect in potassium-doped p-quinquephenyl. The real part of the ac susceptibility shows exactly same transition temperature as that in dc magnetization, and the imaginary part of nearly zero value after transition implies the realization of zero-resistivity. The crystal structure prediction identifies the superconducting phase as Kp3-quinquephenyl with P2₁ space-group, a layered structure. The occurrence of bipolarons revealed by Raman spectra guarantees potassium metal intercalated into p-quinquephenyl and suggests the important role of this elementary excitation played on superconductivity.