Collective Nature of Orbital Excitations in Layered Cuprates in the Absence of Apical Oxygens
Journal article, 2024

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.
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Published in

Physical Review Letters

0031-9007 (ISSN) 1079-7114 (eISSN)

Vol. 132 Issue 6 art. no 066004

Research Project(s)

Resonant inelastic x-ray scattering to study changes in the HTS phase diagram induced by strain and confinement

Swedish Research Council (VR) (2020-04945), 2021-01-01 -- 2024-12-31.

Categorizing

Subject Categories (SSIF 2011)

Condensed Matter Physics

Identifiers

DOI

10.1103/PhysRevLett.132.066004

PubMed

38394564

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Latest update

2/28/2024