Cooperative coupling of static magnetism and bulk superconductivity in   the stripe phase of La_2-xBa_xCuO_4: Pressure- and doping-dependent studies
  Static spin-stripe order and superconductivity were systematically studied in La_2-xBa_xCuO_4 (0.11 - 0.17) at ambient pressure by means of magnetization and muSR experiments. We find that all the investigated La_2-xBa_xCuO_4 samples exhibit static spin-stripe order and that the quasi two-dimensional superconducting (SC) transition temperature T_c1 and the static spin-stripe order temperature T_so have very similar values throughout the phase diagram. Moreover, the magnetic and the SC properties of the x = 0.155 (LBCO-0.155) and x = 0.17 (LBCO-0.17) samples were studied under hydrostatic pressure. As a remarkable result, in these bulk cuprate superconductors the three-dimensional SC transition temperature T_c and T_so nearly coincide at all pressure investigated (0 - 2.3 GPa). We also observed a pressure induced transition from long-range spin stripe order to a disordered magnetic state at 1.6 GPa in LBCO-0.155, coexisting with a SC state with substantial superfluid density. In LBCO-0.17 a disordered magnetic state is present at all p. The present results indicate that static magnetic order and SC pairing correlations develop in a cooperative fashion in La_2-xBa_xCuO_4, and provide a new route of understanding the complex interplay between static magnetism and superconductivity in the stripe phase of cuprates. 
Z. Guguchia, R. Khasanov, A. Shengelaya, E. Pomjakushina, S.J.L.   Billinge, A. Amato, E. Morenzoni, H. Keller
cond-mat.supr-con