Field independent vortex solid-to-liquid transition for B‖ ab in oxygen deficient single crystals of YBa 2Cu 3O 7−δ

Abstract

Single crystals of YBa 2Cu 3O 7−δ provide a suitable test system for vortex dynamics in high temperature superconductors, since the electrical anisotropy γ = ( m c / m ab ) 1 2 can easily be varied over a large range by changing the oxygen content. In this paper the vortex solid-to-liquid transition, as determined from a vortex-glass analysis of the resistivity, has been studied for magnetic fields 0< B≤12 T parallel with the ab plane of oxygen deficient single crystals of YBCO. Strikingly, for high magnetic fields a field independent vortex solid-to-liquid transition is observed. A possible explanation for this phenomenon involving a crossover to a two-dimensional (2D) system is suggested.