Scaling of the vortex-liquid resistivity in optimally doped and oxygen-deficient YBa₂Cu₃O_7-δ single crystals

The consequences of a recently proposed model [A. Rydh, Ö. Rapp, and M. Andersson, Phys. Rev. Lett. 83, 1850 (1999)] for the vortex-liquid resistivity close to a vortex liquid-to-glass transition are analyzed in detail. We find a detailed quantitative agreement between the model and resistivity measurements on disordered, optimally doped YBa₂Cu₃O_7-δ single crystals. For temperatures below the superconducting transition temperature, a scaling of all measured resistivity curves in magnetic field (0<B<~12 T) is obtained. Possible ways of slightly modifying the model in order to fully describe resistivity measurements on more anisotropic underdoped oxygen-deficient YBa₂Cu₃O_7-δ single crystals are suggested. The physical interpretation of the model and its connection to other models of the vortex-liquid resistivity are discussed. In particular, we find close connections to vortex glass models and to a generalized Coulomb gas model.