Dynamic critical properties of the vortex-glass transition derived from angular-dependent properties of La_2-xSr_xCuO₄ films

We present resistivity data on a high-quality La2-xSrxCuO4-δ film measured in a magnetic field of 1 T applied at an angle δ to the c axis. Using these data, the influence of the orientation of the magnetic field and the effective mass anisotropy on the vortex-glass transition can be studied. The variation of δ for a fixed magnitude of the magnetic field allows us to investigate the critical properties of interest, including the 2D-to-3D crossover and the 3D vortex glass-to-fluid transition, as the temperature is decreased. The data are well described by the scaling theory for the d.c. resistivity of an anisotropic superconductor in a magnetic field applied at an angle δ to the c axis. This scaling includes the critical properties close to and at the vortex-glass transition. The main results include (i) evidence of a Kosterlitz-Thouless transition in zero field, and (ii) a 2D-to-3D crossover at H=1 T as the temperature is decreased below the zero-field transition temperature, leading to the vortex fluid-to-vortex glass transition in D=3 characterized by the dynamic critical exponent z≈5.7.