Dynamics of a hole in aCuO4plaquette: Electron energy-loss spectroscopy ofLi2

Abstract

The dynamics of a hole in a CuO4 plaquette: electron energy-loss spectroscopy of Li2CuO2 Atzkern, S.; Knupfer, M.; Golden, M.S.; Fink, J.; Waidacher, C.; Richter, J.; Becker, K.W.; Motoyama, N.; Eisaki, H. Published in:Physical Review B DOI:10.1103/PhysRevB.62.7845 Link to publication Citation for published version (APA):Atzkern, S., Knupfer, M., Golden, M. S., Fink, J., Waidacher, C., Richter, J., ... Eisaki, H. (2000). The dynamics of a hole in a CuO4 plaquette: electron energy-loss spectroscopy of Li2CuO2. Physical Review B, 62, 7845-7849. DOI: 10.1103/PhysRevB.62.7845 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. We have measured the energy-and momentum-dependent loss function of Li 2 CuO 2 single crystals by means of electron energy-loss spectroscopy in transmission. Using the same values for the model parameters, the low-energy features of the spectrum as well as published Cu 2p 3/2 x-ray photoemission data of Li 2 CuO 2 are well described by a cluster model that consists of a single CuO 4 plaquette only. This demonstrates that charge excitations in Li 2 CuO 2 are strongly localized.

Anomalous optical properties of the mixed-valent lithium cuprateLiCu2O2

“…The in-plane charge excitations are localized in the plaquettes and with respect to electronic properties the CuO 4 2− centers in these compounds can be considered to be approximately isolated as in the 0D systems. 14 This point of view is fairly well confirmed in optical and electron energy loss spectra for the monovalent chain cuprate Li 2 Cu 2+ O 2 in which the CuO 2 chains formed by the edge- sharing CuO 4 square plaquettes closely resemble those of the mixed-valent LiCu 2 O 2 . 9 The Li 2 CuO 2 reveals no significant optical absorption features in a wide spectral range up to 4-5 eV.…”

“…15͔͒ is unambiguously assigned to a strong one-center in-plane b 1g → e u ͑ ͒ CT hole transition in CuO 4 square plaquettes. 14 Hence the broadband in the spectral range of 4-5 eV seen in our spectra ͑Figs. 2 and 3͒, rather than the huge resonance at 3.27 eV, may be attributed to an electronic excitation from the O 2p NB band to the UHB.…”

Determining the Short-Range Spin Correlations in the Spin-ChainLi2CuO2andCuGeO3Compounds Using Resonant Inelastic X-Ray Scattering

“…In Li 2 CuO 2 , the situation is more controversial, because in previous experiments with RIXS [22] and other experimental techniques [29][30][31], the ZRS exciton could not be unambiguously observed.…”

Temperature-dependent optical conductivity of undoped cuprates with weak exchange

“…Its missing observation (at T = 300 K) was ascribed to poor resolution 1 , or to uncoupled CuO 4 units. 2 We show, that a ZRS visible at low T would be strongly suppressed at 300 K. However, if the Hamiltonian parameters are chosen to improve the description of O 1s x-ray absorption (XAS) 7 , optical, EELS 1,2 , and RIXS data 5 , then the ZRS absent at T = 0, appears with rising T but is accompanied by a Zhang-Rice triplet (ZRT) contribution at ω ZRT ≈ 4 eV in σ(ω) (superimposed with further transitions). The σ(ω) data are well described this way.…”

“…This will cause a strong T -dependence of various response functions, here presented for the case of the optical conductivity σ(ω). For an illustration of our approach we consider Li 2 CuO 2 being of current interest 1,2,3,4,5,6,7,8,9,10,11,12 , structurally simple, and most importantly, where single crystal data are available in a broad ω-range 1,2 . This system stands for a class of frustrated spin-1/2 chain materials with both small ferromagnetic (FM) NN Cu-Cu exchange coupling J 1 and AFM next-nearest neighbor (NNN) Cu-Cu in-chain exchange J 2 1,3 in terms of a 1D spin-1/2 Heisenberg model…”