EUROPHYSICS LETTERS 15 December 1999 Europhys. Lett., 48 (6), pp. 679-685 (1999) Pure 2D vortex-glass phase transition with T g =0K in deoxygenated YBa 2 Cu 3 O 6.4 thin films Z. Sefrioui 1 , D. Arias( ∗ ) 1 , M. Varela 2 , M. A. L´ opez de la Torre 3 , C. Le´ on 1 G. D. Loos 1 and J. Santamar´ ıa( ∗∗ ) 1 1 Departamento de F´ ısica Aplicada III, Universidad Complutense de Madrid 28040, Madrid, Spain 2 Departamento de F´ ısica, Universidad Carlos III de Madrid Legan´ es 28911, Madrid, Spain 3 Departamento de F´ ısica Aplicada, Universidad de Castilla-La Mancha 13071 Ciudad Real, Spain (received 14 July 1999; accepted in final form 19 October 1999) PACS. 74.60Ge – Flux pinning, flux creep, and flux-line lattice dynamics. PACS. 74.60Jg – Critical currents. PACS. 74.72Fq – Tl-based cuprates. Abstract. – Non-linear I -V characteristics have been measured on high-quality deoxygenated YBa 2Cu3O6.4 thin films, in magnetic fields up to 8 T. Critical scaling analysis of the current- voltage data demonstrates the existence of a pure two-dimensional vortex-glass transition with T g = 0 for high magnetic fields (7, 8 T). The validity of the pure 2D vortex-glass model in our samples is checked with the linear resistivity term and the non-linear current density. The linear resistivity ρ lin (T ) ∝ exp[−(T0/T ) p ] from resistivity vs. temperature and current-voltage measurements, produces the parameters p (p =0.78 for H = 7 T, p =0.73 for H = 8 T) and T0 (230 K) used for the scaling analysis. The non-linear current density j nl exhibits a power law temperature dependence j nl (T ) ∝ T 3 suggesting ν2D = 2 as predicted by the 2D vortex-glass theory. The values of the exponent p obtained in this study are in good agreement with the predictions of the quantum theory of vortex tunneling. Short coherence lengths and large values of the anisotropy are the main factors responsible for the high complexity of the vortex phase diagram of the high-temperature superconductors (HTS). As a result, the dynamic behavior of the vortex system is strongly affected by the combined effects of thermal fluctuations and pinning [1]. In thin films disorder destroys the long-range order of the Abrikosov lattice and stabilizes a vortex-glass (VG) state at low temperatures [2-4], in which dissipation takes place through thermal activation of vortices over ( * ) On leave from Universidad del Quindio, Armenia, Colombia. ( ** ) E-mail: jacsan@eucmax.sim.ucm.es c  EDP Sciences