Melting of Charge Stripes in Vibrationally Driven La1.875Ba0.125CuO4:   Assessing the Respective Roles of Electronic and Lattice Order in Frustrated   Superconductors
  We report femtosecond resonant soft X-ray diffraction measurements of the dynamics of the charge order and of the crystal lattice in non-superconducting, stripe-ordered La1.875Ba0.125CuO4. Excitation of the in-plane Cu-O stretching phonon with a mid-infrared pulse has been previously shown to induce a transient superconducting state in the closely related compound La1.675Eu0.2Sr0.125CuO4. In La1.875Ba0.125CuO4, we find that the charge stripe order melts promptly on a sub-picosecond time scale. Surprisingly, the low temperature tetragonal distortion is only weakly reduced, reacting on significantly longer time scales that do not correlate with light-induced superconductivity. This experiment suggests that charge modulations alone, and not the LTT distortion, prevent superconductivity in equilibrium. 
M. F\"orst, R.I. Tobey, H. Bromberger, S.B. Wilkins, V. Khanna, A.D.   Caviglia, Y.-D. Chuang, W.S. Lee, W.F. Schlotter, J.J...
cond-mat.supr-con