|| Checking for direct PDF access through Ovid
We report detailed studies of the superconducting and normal-state transport properties in NdBa2Cu3O7−y, Nd0.9Ca0.1Ba2Cu3O7−y, and Nd0.8Pr0.2Ba2Cu3O7−y, systems. We found a linear temperature dependence of resistivity ρ and the Hall number nH above Tc. For a given sample ρ∝nH, which is inconsistent with any simple transport model in science (ρ∝1/n). However, ρ and nH at a fixed temperature for these three samples follow a relation ρ∝1/nH. This is evidence that nH could scale with actual mobile carrier concentration. The unit cell volume V is a linear function of nH. The Tc−V−nH diagram indicates that there exist an optimal concentration nH and an optimal V for Tc in these systems.