Electrical Resistivity Anisotropy from Self-Organized One Dimensionality in High-Temperature Superconductors

We investigate the manifestation of stripes in the in-plane resistivity anisotropy in untwinned single crystals of La_2-xSr_xCuO₄ ( x = 0.02–0.04) and YBa₂Cu₃O_y ( y = 6.35–7.0). It is found that both systems show strongly temperature-dependent in-plane anisotropy in the lightly hole-doped region and that the anisotropy in YBa₂Cu₃O_y grows with decreasing y below ∼6.60 despite the decreasing orthorhombicity, which gives most direct evidence that electrons self-organize into a macroscopically anisotropic state. The transport is found to be easier along the direction of the spin stripes already reported, demonstrating that the stripes are intrinsically conducting in cuprates.