High-field generic phase diagram of high-temperature superconductors

Abstract

The temperature-dependent resistivity of (Y 1− z Pr z )Ba 2Cu 3O x epitaxial thin films has been measured in zero-field and at very-high-pulsed magnetic fields (F. Herlach et al., Physica B 216 (1996) 161). It is shown that the zero-field normal-state resistivity above T c for various levels of hole doping p for the (Y 1− z Pr z )Ba 2Cu 3O x cuprate superconductors can be scaled onto one single universal curve (B. Wuyts et al., Phys. Rev. B 53 (1996) 9418). An energy scale Δ, the resistivity ρ Δ and the residual resistivity ρ 0 are suitable scaling parameters. The universal curve exhibits a first region (I) of linear ρ( T) at high temperatures T> T*, a super-linear ρ( T) region at intermediate temperatures T MI< T< T* (II) and a low-temperature insulating-like ρ( T) region (III) at T< T MI. This low-temperature regime is masked by the onset of superconductivity at T= T c. The existence of a universal metallic ρ( 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 allowed suppressing the superconducting state thus retaining the normal-conducting high-field normal-state properties. Our experiments revealed that the ground state of YBa 2Cu 3O x (for x<6.8) is of an insulating nature with the resistivity increasing as temperature is lowered (G.S. Boebinger et al., Phys. Rev. Lett. 77 (1996) 5417; Y. Ando et al., Phys. Rev. Lett. 77 (1996) 2065; 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. Moshchalkov et al., Europhys. Lett. 46 (1999) 75).