Physical Review B vol:6418 issue:18 pages:4425,NIL-4425,NIL
We report on the temperature dependent resistivity of YBa2Cu3Ox and (Y0.6Pr0.4)Ba2Cu3Ox epitaxial thin films, measured in pulsed magnetic fields up to 50 T The zero-field rho (T) data for various levels of hole doping p can be scaled onto one single universal curve by using a linear transformation of both temperature and resistivity. This universal curve exhibits a linear rho (T) at high temperatures T > T* (region I) and a superlinear rho (T) at intermediate temperatures T-MI < T < T* (region II). The ground state in the low temperature region T < T-MI (region III) is masked by the presence of superconductivity below T-c, but is accessible in high magnetic fields. The high field measurements reveal that YBa2Cu3Ox (for x < 6.8) and (Y0.6Pr0.4)Ba2Cu3Ox (for all levels of oxygen content) have an "insulatinglike" ground state at low temperatures and that the universal scaling may be extended to region III. The existence of a universal rho (T) curve indicates that the same mechanisms are dominating the scattering of the charge carriers in these materials but with a different energy scale depending on the carrier concentration and/or the defect structure.