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Your search keyword '"Krockenberger Y"' showing total 2 results
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2 results on '"Krockenberger Y"'

1. Epitaxial growth of Gd₂₋ₓCeₓCuO₄ thin films

Author

Krockenberger, Y., Kurian, J., Naito, M., Alff, L., Krockenberger, Y., Kurian, J., Naito, M., and Alff, L.

Abstract

We have grown (001)-oriented thin films of Gd₂₋ₓCeₓCuO₄ with cerium composition 0 < x < 0.2 by state-of-the-art reactive molecular beam epitaxy and characterized them by x-ray diffraction and transport measurements. A systematical change in the c-axis length upon cerium doping indicates that single-phase films were obtained for the whole doping range. Based on a log po₂ - 1/T phase diagram in combination with reflection high energy electron diffraction (RHEED), phase stability has been determined in order to achieve optimized reduction conditions. Gd₂₋ₓCeₓCuO₄ thin films even after controlled reductions treatment did not show superconductivity in the whole range of Ce concentration studied. However, the room temperature resistivity of optimally reduced Gd₂₋ₓCeₓCuO₄ thin films shows a minimum at around xCe = 0.16. Our results on the growth and characterization of Gd₂₋ₓCeₓCuO₄ thin films on (100) SrTiO3 substrates are described in detail.

Published
2024

2. Collective Nature of Orbital Excitations in Layered Cuprates in the Absence of Apical Oxygens.

Author

Martinelli L, Wohlfeld K, Pelliciari J, Arpaia R, Brookes NB, Di Castro D, Fernandez MG, Kang M, Krockenberger Y, Kummer K, McNally DE, Paris E, Schmitt T, Yamamoto H, Walters A, Zhou KJ, Braicovich L, Comin R, Sala MM, Devereaux TP, Daghofer M, and Ghiringhelli G

Abstract

We have investigated the 3d orbital excitations in CaCuO&#95;{2} (CCO), Nd&#95;{2}CuO&#95;{4} (NCO), and La&#95;{2}CuO&#95;{4} (LCO) using high-resolution resonant inelastic x-ray scattering. In LCO they behave as well-localized excitations, similarly to several other cuprates. On the contrary, in CCO and NCO the d&#95;{xy} orbital clearly disperses, pointing to a collective character of this excitation (orbiton) in compounds without apical oxygen. We ascribe the origin of the dispersion as stemming from a substantial next-nearest-neighbor (NNN) orbital superexchange. Such an exchange leads to the liberation of the orbiton from its coupling to magnons, which is associated with the orbiton hopping between nearest neighbor copper sites. Finally, we show that the exceptionally large NNN orbital superexchange can be traced back to the absence of apical oxygens suppressing the charge transfer energy.

Published
2024
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