Gretarsson, H.*; Nomura, Takuji; Jarrige, I.*; Lupascu, A.*; Upton, M. H.*; Kim, J.*; Casa, D.*; Gog, T.*; Yuan, R. H.*; Chen, Z. G.*; et al.
Physical Review B, 91(24), p.245118_1 - 245118_8, 2015/06
Jarrige, I.*; Kotani, Akio*; Yamaoka, Hitoshi*; Tsujii, Naohito*; Ishii, Kenji; Upton, M.*; Casa, D.*; Kim, J. H.*; Gog, T.*; Hancock, J. N.*
Physical Review Letters, 114(12), p.126401_1 - 126401_5, 2015/03
Wakimoto, Shuichi; Ishii, Kenji; Kimura, Hiroyuki*; Ikeuchi, Kazuhiko*; Yoshida, Masahiro*; Adachi, Tadashi*; Casa, D.*; Fujita, Masaki*; Fukunaga, Yasushi*; Gog, T.*; et al.
Physical Review B, 87(10), p.104511_1 - 104511_7, 2013/03
Jarrige, I.*; Nomura, Takuji; Ishii, Kenji; Gretarsson, H.*; Kim, Y.-J.*; Kim, J.*; Upton, M.*; Casa, D.*; Gog, T.*; Ishikado, Motoyuki*; et al.
Physical Review B, 86(11), p.115104_1 - 115104_4, 2012/09
We report the first observation by momentum-resolved resonant inelastic X-ray scattering of charge excitations in an iron-based superconductor and its parent compound, PrFeAsO and PrFeAsO respectively, with two main results. First, using calculations based on a 16 band model, we show that the energy of the lowest-lying excitations, identified as interband transitions of dominant , orbital character, exhibits a dramatic dependence on electron correlation. This enables us to estimate the Coulomb repulsion and Hund's coupling , and to highlight the role played by in these peculiar orbital-dependent electron correlation effects. Second, we show that short-range antiferromagnetic correlations, which are a prerequisite to the occurrence of these excitations at the point, are still present in the superconducting state.
Ellis, D. S.*; Kim, J.*; Hill, J. P.*; Wakimoto, Shuichi; Birgeneau, R. J.*; Shvyd'ko, Y.*; Casa, D.*; Gog, T.*; Ishii, Kenji; Ikeuchi, Kazuhiko*; et al.
Physical Review B, 81(8), p.085124_1 - 085124_12, 2010/02
Lu, L.*; Hancock, J. N.*; Chabot-Couture, G.*; Ishii, Kenji; Vajk, O. P.*; Yu, G.*; Mizuki, Junichiro; Casa, D.*; Gog, T.*; Greven, M.*
Physical Review B, 74(22), p.224509_1 - 224509_9, 2006/12
We present a detailed Cu -edge resonant inelastic X-ray scattering (RIXS) study of the Mott insulator LaCuO in the 1-7 eV energy loss range. As initially found for the high-temperature superconductor HgBaCuO, the spectra exhibit a multiplet of weakly dispersive electron-hole excitations, which are revealed by utilizing the subtle dependence of the cross section on the incident photon energy. The close similarity between the fine structures for in-plane and out-of-plane polarizations is indicative of the central role played by the 1s core hole in inducing charge excitations within the CuO planes. On the other hand, we observe a polarization dependence of the spectral weight, and careful analysis reveals two separate features near 2 eV that may be related to different charge-transfer processes. The polarization dependence indicates that the electrons contribute significantly to the RIXS cross section.
Wakimoto, Shuichi; Kim, Y.-J.*; Kim, H.*; Zhang, H.*; Gog, T.*; Birgeneau, R. J.*
Physical Review B, 72(22), p.224508_1 - 224508_7, 2005/12
Resonant inelastic X-ray scattering (RIXS) at the copper Kabsorption edge has been performed for heavily overdoped samplesof LaSrCuO with and . We have observed the chargetransfer and molecular orbital excitations which exhibit resonances at incident energies of and keV,respectively. From a comparison with previous results on undoped andoptimally-doped samples, we determine that the charge transfer excitation energy increases monotonically as doping increases. In addition, the -dependences of the RIXS spectral weight and absorption spectrum exhibit no clear peak at keV in contrast to results in the underdoped samples. The low-energy ( eV) continuum excitation intensity has been studied utilizing the high energy resolution of 0.13 eV (FWHM). A comparison of the RIXS profiles at and indicates that the continuum intensity exists even at in the overdoped samples, while it has been reported only at and for the sample. Furthermore, we also found an additional excitation on top of the continuum intensity at the and positions.