Two-Dimensional Superconducting Fluctuations in Stripe-Ordered La_1.875Ba_0.125CuO₄

Recent spectroscopic observations of a d-wave-like gap in stripe-ordered La_2-xBa_xCuO₄ with x=1/8 have led us to critically analyze the anisotropic transport and magnetization properties of this material. The data suggest that concomitant with the spin ordering is an electronic decoupling of the CuO₂ planes. We observe a transition (or crossover) to a state of two-dimensional (2D) fluctuating superconductivity, which eventually reaches a 2D superconducting state below a Berezinskii-Kosterlitz-Thouless transition. Thus, it appears that the stripe order in La_2-xBa_xCuO₄ frustrates three-dimensional superconducting phase order, but is fully compatible with 2D superconductivity and an enhanced T_c.