Emergent transition for superconducting fluctuations in antiferromagnetic ruthenocuprates

The emergence of carrier pairing from the electronically inhomogeneous phase of lightly hole-doped copper oxides has been investigated through magnetoresistance measurements on 1222-type ruthenocuprates RuSr2(R,Ce)(2)Cu2O10-delta, principally with R = Gd, Sm, Nd. A well-defined transition at which superconducting fluctuations emerge is discovered at a remarkably low critical doping, p(c) = 0.0084, deep within the antiferromagnetic phase. Systematic variations of the low-temperature fluctuation density with doping and cell volume demonstrate the intrinsic nature of the electronic inhomogeneity and provide new support for bosonic models of the superconducting mechanism.