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

@ARTICLE{Martinelli2024,
	author = {Martinelli, Leonardo and Wohlfeld, Krzysztof and Pelliciari, Jonathan and Arpaia, Riccardo and Brookes, Nicholas B. and Di Castro, Daniele and Fernandez, Mirian G. and Kang, Mingu and Krockenberger, Yoshiharu and Kummer, Kurt and McNally, Daniel E. and Paris, Eugenio and Schmitt, Thorsten and Yamamoto, Hideki and Walters, Andrew and Zhou, Ke-Jin and Braicovich, Lucio and Comin, Riccardo and Sala, Marco Moretti and Devereaux, Thomas P. and Daghofer, Maria and Ghiringhelli, Giacomo},
	title = {Collective Nature of Orbital Excitations in Layered Cuprates in the Absence of Apical Oxygens},
	year = {2024},
	journal = {Physical Review Letters},
	volume = {132},
	number = {6},
	doi = {10.1103/PhysRevLett.132.066004},
	url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85184856519&doi=10.1103%2fPhysRevLett.132.066004&partnerID=40&md5=0b788da6d9f31c5708086307160483dc},
	abstract = {We have investigated the 3d orbital excitations in CaCuO2 (CCO), Nd2CuO4 (NCO), and La2CuO4 (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 dxy 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.  © 2024 American Physical Society.},
	keywords = {Calcium compounds; Charge transfer; Lanthanum compounds; Neodymium compounds; X ray scattering; Apical oxygen; High resolution; La2CuO4; Layered cuprates; Localized excitations; Nearest-neighbour; Orbital excitations; Orbitals; Resonant inelastic x-ray scattering; Superexchanges; Copper compounds},
	type = {Article},
	publication_stage = {Final},
	source = {Scopus},
	note = {Cited by: 0; All Open Access, Green Open Access}
}