Scaling of vortex transport properties in high-temperature superconductors

Using both dc and low-frequency-ac (10–${10}^5$ Hz) transport measurements in low magnetic fields (0–6.3 kOe), we find that the vortex transport properties of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_{2.98}$ ${\mathrm{Au}}_{0.02}$ ${\mathrm{O}}_{\mathit{x}}$ (x=6.97±0.02) single crystals are consistent with a three-dimensional second-order vortex solid melting transition, with a static exponent ν=0.9±0.2, a dynamic exponent z=2.0±0.2, and a characteristic current-density exponent μ=0.5±0.1. In contrast, transport properties of epitaxial films generally agree with the Ambegaokar-Halperin model.