In this talk I will first discuss a novel combined scanning tunneling microscopy (STM) and resonant X‑ray scattering (RXS) experimental approach that established the formation of CO in the high-temperature superconductor Bi2Sr2CaCu2O8+x (Bi-2212) . The CO in this system occurs with the same period as those found in Y-based or La-based cuprates and displays the analogous competition with superconductivity, therefore establishing its commonality to hole-doped cuprates. Still, the universality of charge order remained in question, with several experiments and theories pointing to hole-doping as a critical ingredient to its formation.
Here I will also present RXS measurements that demonstrated for the first time the presence of charge order in the electron-type cuprate Nd2-xCexCuO4 (NCCO) . A comprehensive study of CO in NCCO as a function of doping, temperature, and magnetic fields, shows that CO does not require a pseudogap precursor state. We also find that while CO is universal to all cuprates, its interplay with superconductivity and antiferromagnetism is not. Finally, open questions in the field, as well as prospects for future experiments, will also be discussed.
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