Molecular orbital excitations in cuprates: Resonant inelastic x-ray scattering studies

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Y.J. Kim, J.P. Hill, G.D. Gu, F.C. Chou, S. Wakimoto, R.J. Birgeneau, S. Komiya, Y. Ando, N. Motoyama, K.M. Kojima, S. Uchida, D. Casa, T. Gog

Abstract:
We report resonant inelastic x-ray scattering studies of electronic excitations in a wide variety of cuprate compounds. Specifically, we focus on the charge-transfer type excitation of an electron from a bonding molecular orbital to an antibonding molecular orbital in a copper oxygen plaquette. Both the excitation energy and the amount of dispersion are found to increase significantly as the copper oxygen bond length is reduced. We also find that the estimated bond-length dependence of the hopping integral t(pd) is much stronger than that expected from tight-binding theory.