The unoccupied electronic structure for the Sr14Cu24O41 family of two-leg ladder compounds was investigated for different partial substitutions of Sr2+ by Ca2+, leaving the nominal hole count constant, and by Y3+ or La3+, reducing the nominal hole count from its full value of 6 per formula unit. Using polarization-dependent x-ray absorption spectroscopy on single crystals, hole states on both the chain and ladder sites could be studied. While for intermediate hole counts all holes reside on O sites of the chains, a partial hole occupation on the ladder sites in orbitals oriented along the legs is observed for the fully doped compound Sr14Cu24O41. On substitution of-Ca for Sr orbitals within the ladder planes but perpendicular to the legs receive some hole occupation as well.
Publication Source (Journal or Book title)
Physical Review B - Condensed Matter and Materials Physics
Nücker, N., Merz, M., Kuntscher, C., Gerhold, S., Schuppler, S., Neudert, R., Golden, M., Fink, J., Schild, D., Stadler, S., Chakarian, V., Freeland, J., Idzerda, Y., Conder, K., Uehara, M., Nagata, T., Goto, J., Akimitsu, J., Motoyama, N., Eisaki, H., Uchida, S., Ammerahl, U., & Revcolevschi, A. (2000). Hole distribution in (Sr, Ca, Y, La) 14Cu24O41 ladder compounds studied by x-ray absorption spectroscopy. Physical Review B - Condensed Matter and Materials Physics, 62 (21), 14384-14392. https://doi.org/10.1103/PhysRevB.62.14384