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Tsutsui, Kenji; Kaneshita, Eiji*; Toyama, Takami*
Physical Review B, 92(19), p.195103_1 - 195103_5, 2015/11
Times Cited Count：2 Percentile：9.39(Materials Science, Multidisciplinary)Nonresonant inelastic X-ray scattering (NIXS) is a possible tool to detect charge excitations in electron systems. In addition, multipole transitions at high-momentum-transfer region open a new possibility to determine orbital-selective electronic excitations in multi-orbital itinerant 3
electron systems. As a theoretical example, we chose the antiferromagnetic state of iron arsenides and demonstrate that the orbital-selective excitations are detectable by choosing appropriate momentum transfer in NIXS. We propose that both NIXS and resonant inelastic X-ray scattering are complementary to each other for fully understanding the nature of orbital excitations in multi-orbital itinerant electron systems.
Sugimoto, Kodai*; Toyama, Takami*; Kaneshita, Eiji*; Tsutsui, Kenji
Journal of the Korean Physical Society, 63(3), p.632 - 635, 2013/08
Times Cited Count：0 Percentile：0.00(Physics, Multidisciplinary)Cr is the representative material of multi-orbital antiferromagnetism. We numerically calculate the band structure and density of states in commensurate antiferromagnetic Cr by multi-orbital Hubbard model with mean-field approximation. The result is adopted to the calculation of optical conductivity. The spectra of the optical conductivity is consistent with experimental data, and this promises the validity of our model.
Sugimoto, Kodai*; Li, Z.*; Kaneshita, Eiji*; Tsutsui, Kenji; Toyama, Takami*
Physical Review B, 87(13), p.134418_1 - 134418_8, 2013/04
Times Cited Count：7 Percentile：32.24(Materials Science, Multidisciplinary)We theoretically investigate spin dynamics and L-edge resonant inelastic X-ray scattering (RIXS) of chromiumwith commensurate spin-density wave (SDW) order, based on a multiband Hubbard model. Obtaining the ground state with the SDW mean-field approximation, we calculate the dynamical spin susceptibility by using random-phase approximation. We find that a collectivespin-wave excitation hardly damps up to 0.6 eV. Above the energy, the excitation overlaps individual particle-hole excitations, leading to broad spectral weight.
Nomura, Takuji; Kaneshita, Eiji*
Journal of the Physical Society of Japan, 81(2), p.024707_1 - 024707_11, 2012/02
Times Cited Count：2 Percentile：18.88(Physics, Multidisciplinary)We analyze theoretically the resonant inelastic X-ray scattering (RIXS) at the Ni 
edge in the stripe-ordered state of La
Sr
NiO
at 
= 1/3. In the calculation of RIXS spectra, the stripe-ordered ground state is described within the Hartree-Fock approximation by using a realistic tight-binding model for Ni 3
and O 2
orbitals, and the electron correlations in the electronic excitation processes are taken into account within the random-phase approximation. The calculated RIXS spectrum shows a tail toward the low-energy region when the momentum transfer of photons equals the stripe vector 
, being consistent with a recent experimental result. The origin of this anomalous momentum dependence of RIXS spectra is discussed microscopically.
Sugimoto, Kodai*; Kaneshita, Eiji*; Tsutsui, Kenji; Toyama, Takami*
no journal, ,
Chromium is representative material of multi-orbital anriferromagnetism. We calculate the electronic state by multi-orbital Hubbard model with mean-field approximation. Using the states, we also calculate the L-edge resonant inelastic X-ray scattering spectra with first-collision approximation. We discuss characteristic spectral features.
Tsutsui, Kenji; Kaneshita, Eiji*; Toyama, Takami*
no journal, ,
We discuss theoretically the electronic excitations in parent system of iron arsenide superconductors by non-resonant inelastic X-ray scattering. In particular, the features of the excitation spectra due to the multi-pole transitions are predicted.
Sugimoto, Kodai*; Zhi, L.*; Kaneshita, Eiji*; Tsutsui, Kenji; Toyama, Takami*
no journal, ,
Chromium is a representative metal with spin density wave. In this study, spin excitation and L-edge resonant inelastic X-ray scattering spectra are obtained theoretically by using the multi-orbital Hubbard model with mean-field, randam phase, and first collision approximations.
Nomura, Takuji; Kaneshita, Eiji*
no journal, ,
We analyze theoretically the resonant inelastic X-ray scattering (RIXS) at the Ni edge in the stripe-ordered state. In the calculation of RIXS spectra, the stripe-ordered ground state is described within the Hartree-Fock approximation by using a realistic tight-binding model, and the electron correlations in the electronic excitation processes are taken into account within the random-phase approximation. The calculated RIXS spectrum shows a tail toward the low-energy region when the momentum transfer of photons equals the stripe vector, being consistent with a recent experimental result. The origin of this anomalous momentum dependence of RIXS spectra is discussed microscopically.
Kaneshita, Eiji*; Tsutsui, Kenji; Toyama, Takami*
no journal, ,
The ground and excited states in parent systems of iron-pnictide superconductors are discussed by means of the mean-field theory in multi-band Hubbard models. We compare theoretically excitation properties in the double-stripe state of 11-systems and those in the stripe state of 122-systems.
