Dimensionality crossover in Tl2Ba2Ca2Cu3O10-δ compounds in magnetic fields

The I-V characteristics of Tl2Ba2Ca2Cu3O10-δ bulk samples have been measured in magnetic fields (0.07-1.2 T). It is found that at low fields (0.07-0.15 T), The nonlinear I-V curves show scaling behaviors which are consistent with a three dimensional Vortex-Glass phase transition with a dynamic exponent z=2.7. As the magnetic field increases, I-V curves gradually deviate from the typical Vortex-Glass scaling behavior. When H>0.6 T, a pure power-law in the I-V curves could not be found at any temperature, which indicates that a 3D to 2D crossover occurs. (orig.)