High-field generic phase diagram of high-temperature superconductors

The temperature-dependent resistivity of(Y1-zPrz)Ba-2 Cu-3 O-x epitaxial th in films has been measured in zero-field and at very-high-pulsed magnetic f ields (F. Herlach et al., Physica B 216 (1996) 161). It is shown that the z ero-field normal-state resistivity above T-c for various levels of hole dop ing p for the (Y1-zPrz)Ba-2 Cu-3 O-x cuprate superconductors can be scaled onto one single universal curve (B. Wuyts et al., Phys. Rev. B 53 (1996) 94 18). An energy scale Delta, the resistivity rho (Delta) and the residual re sistivity p(0) are suitable scaling parameters. The universal curve exhibit s a first region (I) of linear rho (T) at high temperatures T > T*, a super -linear rho (T) region at intermediate temperatures T-MI < T < T* (II) and a low-temperature insulating-like p(T) region (III) at T < T-MI. This low-t emperature regime is masked by the onset of superconductivity at T = T-c. T he existence of a universal metallic p(T) curve is interpreted as a strong indication of one single mechanism dominating the scattering of the charge carriers in these materials. In order to gain access to the low-temperature T < T-c part of the normal-state transport properties (regions II and III) , experiments in high magnetic fields are performed. These experiments allo wed suppressing the superconducting state thus retaining the normal-conduct ing high-field normal-state properties. Our experiments revealed that the g round state of YBa2Cu3Ox (for x < 6.8) is of an insulating nature with the resistivity increasing as temperature is lowered (G.S. Boebinger et al., Ph ys. Rev. Lett. 77 (1996) 5417; Y. Ando et al., Phys. Rev. Lett. 77 (1996) 2 065; Phys. Rev. B 56 (1997) R8530). All experiments shown in this work are understood as consequences of a low-dimensional quantum transport mechanism in combination with scattering of a magnetic origin (V.V. Moshchalkov, Sol . State Commun. 86 (1993) 715; Cond-Mat/9802281; V.V. MoshchaIkov et al., E urophys. Lett. 46 (1999) 75). <(c)> 2001 Elsevier Science B.V. All rights r eserved.