Optical characteristics of charge carrier transfer across interfaces between YBa2Cu3O6+delta and La0.7Ca0.3MnO3

摘要

We report a spectral ellipsometry study of multilayers composed of superconducting YBa2Cu3O6+delta (YBCO) and ferromagnetic La0.7Ca0.3MnO3 (LCMO) in the spectral range 0.7-6.5 eV. With increasing YBCO sublayer thickness, the optical spectral weight is enhanced at photon energies of 1.5-3.5 eV. The spectral weight enhancement is proportional to the number of interfaces of each multilayer sample, indicating its association with the interfacial electronic structure. Based on calculations in the framework of a multilayer model, we find that the shape of the interface-induced spectral weight is consistent with transfer of hole carriers from YBCO to LCMO. Our results imply that the holes that are transferred across the interfaces accumulate in the LCMO layers, rather than being pinned by interfacial defects or annihilated by electron donors such as oxygen vacancies. Optical spectroscopy can thus serve as a nondestructive probe of charge transfer across buried interfaces in metal-oxide heterostructures.