Among the cuprate superconductors, the infinite layer compound SrCuO2 is the one with the simplest crystal structure that can be electron doped (e-doped) by La substitution (Tc≈40K for x=10%). Many difficulties arise in comparing hole (h-doped) and e-doped cuprates with layered structure, as the parent compounds of the two families do not share the same crystal structure. Many differences are observed between the two families, such as different magnetic order in the undoped compounds, stronger antiferromagnetism in the e-doped, more unconventional transport properties in h-doped, different band structure. However it is not clear whether these differences are intrinsic of superconductivity in these compounds. In this respect, infinite layer compounds are interesting, due to their minimal structure, not involving (magnetic!) rare earth charge reservoir blocks of the layered compounds (such as (Nd,Ce)2CuO4). We present x-ray absorption spectroscopy (XAS) measurements at the Cu L2,3 and O K edge on (Sr,La)CuO2 thin films grown by MBE. The measurements have been performed by synchrotron radiation at the APE beamline of ELETTRA lightsource. Samples with different La and O content have been measured at different temperatures ranging from room temperature down to 30K, using linear polarized photons. Strong linear dichroism is observed at both edges, according to the square planar coordination of Cu ions. In h-doped compounds the O K pre-edge is strongly modulated with doping, as the oxygen states are influenced by the density of states at the Fermi level, thus reflecting the deployment of the upper Hubbard band into the conduction band. On the contrary no particular doping dependence is usually observed in e-doped compounds, both layered and infinite layers. However we find some pre-edge modification with La and O content of the samples. The results are interpreted in terms of hole and electron doping of the compound by either oxygen defects or La.

XAS measurements and linear dichroism at the Cu L2,3 and O K edge on infinite layer e-doped superconductors

GALDI, ALICE;MARITATO, Luigi;
2014

Abstract

Among the cuprate superconductors, the infinite layer compound SrCuO2 is the one with the simplest crystal structure that can be electron doped (e-doped) by La substitution (Tc≈40K for x=10%). Many difficulties arise in comparing hole (h-doped) and e-doped cuprates with layered structure, as the parent compounds of the two families do not share the same crystal structure. Many differences are observed between the two families, such as different magnetic order in the undoped compounds, stronger antiferromagnetism in the e-doped, more unconventional transport properties in h-doped, different band structure. However it is not clear whether these differences are intrinsic of superconductivity in these compounds. In this respect, infinite layer compounds are interesting, due to their minimal structure, not involving (magnetic!) rare earth charge reservoir blocks of the layered compounds (such as (Nd,Ce)2CuO4). We present x-ray absorption spectroscopy (XAS) measurements at the Cu L2,3 and O K edge on (Sr,La)CuO2 thin films grown by MBE. The measurements have been performed by synchrotron radiation at the APE beamline of ELETTRA lightsource. Samples with different La and O content have been measured at different temperatures ranging from room temperature down to 30K, using linear polarized photons. Strong linear dichroism is observed at both edges, according to the square planar coordination of Cu ions. In h-doped compounds the O K pre-edge is strongly modulated with doping, as the oxygen states are influenced by the density of states at the Fermi level, thus reflecting the deployment of the upper Hubbard band into the conduction band. On the contrary no particular doping dependence is usually observed in e-doped compounds, both layered and infinite layers. However we find some pre-edge modification with La and O content of the samples. The results are interpreted in terms of hole and electron doping of the compound by either oxygen defects or La.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11386/4565272
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