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 CuO2 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, nickelate and cobaltate systems by neutron or x ray diffraction. For the prototypical high temperature superconductor La2 xSrxCuO4 LSCO no charge stripe signal has been found so far, but there are several indications for a proximity to the formation of charge stripes. Here we report the observation of a pronounced charge stripe signal in the near surface region of 12 percent doped LSCO. From our experimental results we conclude that this compound is sufficiently close to the formation of charge stripes 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 LSCO should be relevant for the interpretation of data from surface sensitive probes like photoelectron spectroscopy or scanning tunnelling spectroscopy, which are widely used to study LSCO and similar systems