Coupled Cu and Mn charge and orbital orders in YBa2Cu3O7/Nd0.65(Ca1-ySry)0.35MnO3 multilayers

The observation of a charge density wave in the underdoped cuprate high T c superconductors (Cu-CDW) raised a debate about its relationship with superconductivity. In bulk YBa 2 Cu 3 O 7− δ the Cu-CDW is incipient and mainly pinned by defects. Nevertheless, a large magnetic field can induce a true long-range Cu-CDW order as it suppresses superconductivity. An enhanced Cu-CDW order was also observed in YBa 2 Cu 3 O 7 /La 2/3 Ca 1/3 MnO 3 multilayers. Here, we show that the magnitude of the Cu-CDW in YBa 2 Cu 3 O 7− δ / Nd 0.65 (Ca 1-y Sr y ) 0.35 MnO 3 multilayers can be varied by adjusting the strength of the manganite charge and orbital order via the Sr content (tolerance factor). Furthermore, we resolve the reconstruction of the crystal field levels of the interfacial Cu ions that are also affected by the manganite charge and orbital order. This tuneable interfacial coupling and Cu-CDW in YBa 2 Cu 3 O 7− δ can be used for studying the relationship between the Cu-CDW and superconductivity and, possibly, for inducing new intertwined quantum states. The relationship between superconductivity and charge density waves is one of the unresolved mysteries of high temperature cuprate superconductors. The authors investigate this relationship using multilayers of cuprates and manganites for which the charge and orbital order of the latter is controlled by chemical substitution.