Abstract
Electronic spin and orbital excitation spectra of ) samples are measured by resonant inelastic x-ray scattering (RIXS). In this compound, of samples with identical hole dopings is strongly affected by the Ca/Ba substitution due to subtle variations in the lattice constants, while crystal symmetry and disorder as measured by linewidths are independent. We examine two extreme values of and two extreme values of hole-doping content corresponding to antiferromagnetic and superconducting states. The dependence of the spin-mode energies is approximately the same for both the antiferromagnetic and superconducting samples. This clearly demonstrates that RIXS is sensitive to the superexchange even in doped samples. A positive correlation between and the maximum of at optimal doping is observed. We also measured the dependence of the and orbital splittings. We infer that the effect of the unresolved excitation on is much smaller than the effect of . There appears to be dispersion in the peak of up to 0.05 eV. Our fitting furthermore indicates an asymmetric dispersion for the excitation. A peak at eV is also observed and attributed to a excitation in the chain layer.
6 More- Received 31 December 2014
- Revised 11 June 2015
DOI:https://doi.org/10.1103/PhysRevB.92.104507
©2015 American Physical Society