Field-induced crossover of criticalities of vortex dynamics in Tl ₂ Ba ₂ CaCu ₂ O ₈ thin films

Abstract

By analyzing I-V characteristics (E-j curves), which were experimentally determined on Tl2Ba2CaCu2O8 thin films in magnetic fields Be varying from 0 T to 5 T, we find that the transition of the linear resistivity ρlin = [E/j]j → 0 signaling superconductivity exhibits different criticalities for different magnetic fields. Starting with a Berezinskii-Kosterlitz-Thouless transition at TBKT = 103.7 K for Be = 0 T, one induces a crossover to a quasi-2D or 3D vortex-glass transition at a finite Tg for magnetic fields below a few kOe, and finally a "true" 2D vortex-glass with Tg = 0 K for higher fields. We argue that this field-induced crossover of criticalities is a general feature of all strongly anisotropic high-Tc superconductors.