Precursor Charge Density Waves in La1.875Ba0.125CuO4*

The observation of charge density wave (CDW) correlations in numerous different samples has provided increasing support to the concept that these correlations are an intrinsic property of the high temperature superconducting cuprates. It has long been hypothesized that long-range CDW order arises from the pinning of precursor high-temperature CDW fluctuations, but while precursor spin density wave (SDW) correlations have been studied in detail, the corresponding transition between long-range ordered and precursor CDW correlations has never been observed. Here, using resonant inelastic x-ray scattering (RIXS), we report the discovery of precursor CDW correlations in La1.875Ba0.125CuO4.