Charge stripe order near the surface of 12-percent doped La2−xSrxCuO4

A collective order of spin and charge degrees of freedom into stripes has been predicted to be a possible ground state of hole-doped CuO 2 planes, which are the building blocks of high-temperature superconductors. In fact, stripe-like spin and charge order has been observed in various layered cuprate systems. For the prototypical high-temperature superconductor La 2− x Sr x CuO 4 , no charge-stripe signal has been found so far, but several indications for a proximity to their formation. Here we report the observation of a pronounced charge-stripe signal in the near surface region of 12-percent doped La 2− x Sr x CuO 4 . We conclude that this compound is sufficiently close to charge stripe formation that small perturbations or reduced dimensionality near the surface can stabilize this order. Our finding of different phases in the bulk and near the surface of La 2− x Sr x CuO 4 should be relevant for the interpretation of data from surface-sensitive probes, which are widely used for La 2− x Sr x CuO 4 and similar systems. Charge stripe order has been predicted to be the ground state for the parent compounds of copper oxide superconductors. Using resonant X-ray diffraction, Schüßler-Lagenheine et al . probe the surface region of 12 percent doped La 2− x Sr x CuO 4 , and observe charge-stripe order.