Ambient-pressure superconductivity of κʹ-(BEDT-TTF)2Cu2(Cn)3 realized by a carrier-doping into a mott-insulating state

By examining the magnetic properties and the band structure, it is revealed that κ -(BEDTTTF) 2CU2(CN)3 is a Mott-insulator with strong dimerization and narrow upper-HOMO-band width. The title compound is the first organic compound in which the superconductivity is realized by the carrier-doping into a Mott-insulator. In this case, a small quantity of Cu2+ substitutes the Cu+ in κ-(BEDT-TTF)2Cu2(CN)3, thus donating electrons into the half-filled upper-HOMO-band. A possible structure around the Cu2+ site is presented.