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論文

Electronic excitations around the substituted atom in La$$_2$$Cu$$_{1-y}$$N$$_y$$O$$_4$$ as seen via resonant inelastic X-ray scattering

石井 賢司; 筒井 健二; 池内 和彦*; Jarrige, I.; 水木 純一郎; 平賀 晴弘*; 山田 和芳*; 遠山 貴己*; 前川 禎通; 遠藤 康夫*; et al.

Physical Review B, 85(10), p.104509_1 - 104509_5, 2012/03

 被引用回数:3 パーセンタイル:16.62(Materials Science, Multidisciplinary)

We perform a resonant inelastic X-ray scattering (RIXS) study of Ni-substituted La$$_2$$CuO$$_4$$ and Cu-substituted La$$_2$$NiO$$_4$$.Resonantly enhanced charge-transfer excitations are successfully observed by tuning the incident photon energy to the $$K$$-edge of the substituted element. These excitations display a very weak momentum dependence, evidencing their local character. We find a shift in the energy of the onset edge of these features compared with the non-substituted compounds La$$_2$$CuO$$_4$$ and La$$_2$$NiO$$_4$$. This shift is quantitatively reproduced by exact diagonalization calculations of the RIXS spectra. RIXS is shown to be a powerful tool to probe the electronic states of substituted elements and to understand their interaction with surrounding atoms.

論文

Resonant inelastic X-ray scattering of La$$_2$$Cu$$_{0.95}$$Ni$$_{0.05}$$O$$_4$$

石井 賢司; 池内 和彦*; Jarrige, I.; 水木 純一郎; 平賀 晴弘*; 山田 和芳*; 筒井 健二; 遠山 貴己*; 前川 禎通*; 遠藤 康夫*; et al.

Physica C, 470(Suppl.1), p.S155 - S157, 2010/12

 被引用回数:0 パーセンタイル:0(Physics, Applied)

Substitution of a specific element for a component is often used to elucidate its role in the superconductors. For a complete understanding of the substitution effect not only on the superconductivity but also on the electronic states, element-selective experiments are required. In this respect, resonant inelastic X-ray scattering (RIXS) has proven to be a powerful experimental technique enabling element-selective diagnosis of charge excitations. By tuning the incident photon energy to a given absorption edge of the element, the excitations involving the element are resonantly enhanced. In addition, RIXS has the advantage that momentum dependence can be measured. Using RIXS, we have measured the electronic excitations at the substituting sites in La$$_2$$Cu$$_{0.95}$$Ni$$_{0.05}$$O$$_4$$ and La$$_2$$Ni$$_{0.95}$$Cu$$_{0.05}$$O$$_4$$. Near the absorption edge of the substituting element, namely the Ni $$K$$-edge for La$$_2$$Cu$$_{0.95}$$Ni$$_{0.05}$$O$$_4$$ and the Cu $$K$$-edge for La$$_2$$Ni$$_{0.95}$$Cu$$_{0.05}$$O$$_4$$, charge transfer excitations from the 2$$p$$ level of neighboring oxygen to the upper Hubbard band of the substituted Ni/Cu are observed. Experimental spectra are qualitatively reproduced by a theoretical calculation based on a $$d$$-$$p$$ model.

論文

Thermally activated charge transfer in a Prussian blue derivative probed by resonant inelastic X-ray scattering

Jarrige, I.; Cai, Y. Q.*; 石井 啓文*; 平岡 望*; Bleuzen, A.*

Applied Physics Letters, 93(5), p.054101_1 - 054101_3, 2008/08

 被引用回数:9 パーセンタイル:38.53(Physics, Applied)

Charge-transfer excitation is at the source of the photoinduced magnetism observed in several Prussian blue molecule-based magnets. Using resonant inelastic X-ray scattering and X-ray absorption spectroscopy, we probe directly the thermally-activated charge transfer in a photomagnetic Fe-Co cyanide, Cs$$_{0.7}$$Co$$_{4}$$[Fe(CN)$$_{6}$$]$$_{2.9}$$[V]$$_{1.1}$$. 16H$$_{2}$$O, where [V] represents [Fe(CN)$$_{6}$$] vacancies. The temperature dependence of both Co and Fe valence ratios is estimated for the first time in one cooling run, thus yielding a more complete picture of the temperature-induced cooperative electronic modifications. This novel approach, benefiting from relatively short acquisition times, opens the possibility for realtime characterization of the photoinduced magnetism in molecule-based magnets.

口頭

Competition between multi-channel Kondo effect and f delocalization in TmTe at high pressure

Jarrige, I.; Rueff, J.-P.*; Shieh, S.*; 田口 宗孝*; 石井 啓文*; Cai, Y. Q.*

no journal, , 

Identifying the mechanism of Kondo phenomena is arguably one of the most exciting and widely studied issues in condensed matter physics. Intermediate-valent Tm compounds stand out as potential candidates for multichannel Kondo (ncK) effect, since both integer valences Tm$$^{2+}$$ and Tm$$^{3+}$$ are magnetic. Using resonant inelastic X-ray scattering and the Anderson impurity model, we probed the Tm valence and 4f-5d hybridization in the high-pressure intermediate-valent TmTe compound. Our results reveal that the f delocalization is discontinuous, characterized by a previously unobserved plateau-like behavior over the 4.3$$sim$$6.5 GPa range. This is at odds with the usual, continuous Kondo-like f delocalization, and is interpreted as an experimental observation of the effect of culminating ncK scattering of d electrons from local moments on the electronic structure.

口頭

Competition between multi-channel Kondo effect and f delocalization in TmTe at high pressure

Jarrige, I.; Rueff, J.-P.*; Cai, Y. Q.*; Shieh, S.*; 石井 啓文*; 田口 宗孝*

no journal, , 

Among numerous f electron systems which present Kondo properties, intermediate-valent Tm compounds stand out as potential candidates for multichannel Kondo (ncK) effect, since both integer valences Tm2+ and Tm3+ are magnetic. Using resonant inelastic X-ray scattering and the Anderson impurity model, we probed the Tm valence and 4f-5d hybridization in the high-pressure intermediate-valent TmTe compound. Our results reveal that the f delocalization is discontinuous, characterized by a previously unobserved plateau-like behavior between the volume collapse transition and the structural transition (4.3$$sim$$6.5 GPa), with an associated valence (2.55) at odds with the near-trivalency previously reported. This is at odds with the usual, continuous Kondo-like f delocalization, and is interpreted as an experimental observation of the effect of culminating ncK scattering of d electrons from local moments on the electronic structure.

口頭

Single-channel vs multi-channel Kondo effects; SmTe and TmTe studied via resonant inelastic X-ray scattering under high pressure

Jarrige, I.; Rueff, J.-P.*; Shieh, S.*; 田口 宗孝*; 大石 泰生*; 松村 武*; 石井 啓文*; 平岡 望*; Cai, Y. Q.*

no journal, , 

Using resonant inelastic X-ray scattering and the Anderson impurity model, we estimated the pressure dependence of the Sm and Tm valence and 4 f -5d hybridization in the respectively single and multi-channel Kondo compounds SmTe and TmTe. We observed a usual, continuous Kondo-like f delocalization for SmTe as a function of pressure. On the contrary, our results reveal that the f delocalization in TmTe is discontinuous, characterized by a previously unobserved plateau-like behavior between 4.3 and 6.5 GPa. This is interpreted as an experimental observation of the effect of culminating multi-channel Kondo scattering of d electrons from local moments on the electronic structure. Our study raises the interesting possibility that an NCK effect realized in a compressed mixed-valent f system could impede the concomitant electron delocalization.

口頭

Electronic excitations probed with resonant inelastic X-ray scattering

石井 賢司; 筒井 健二; 池内 和彦*; Jarrige, I.; 水木 純一郎; 平賀 晴弘*; 山田 和芳*; 遠山 貴己*; 前川 禎通; 石井 啓文*; et al.

no journal, , 

It is widely recognized that inelastic scattering of neutron and X-ray is a powerful tool to investigate dynamical properties of electrons in the energy-momentum space. Especially, inelastic X-ray scattering has become available in the last decade by utilizing brilliant synchrotron radiation X-rays. When the incident X-ray energy is tuned to an absorption edge of a constituent element of materials, resonantly enhanced electronic excitations are observed, which is called resonant inelastic X-ray scattering (RIXS). An additional characteristic arises from the resonant process, namely, the specific element selectively get involved in the observed excitations. While neutron scattering is predominantly sensitive to spin excitations, one can complementarily measure various excitations of electronic degrees of freedom, charge, spin, and orbital, with the RIXS technique. In our presentation, we show an explicit application of the element selectivity: resonant inelastic X-ray scattering of Ni-substituted La$$_{2}$$CuO$$_{4}$$ and Cu-substituted La$$_{2}$$NiO$$_{4}$$. Resonantly enhanced charge-transfer excitations are successfully observed by tuning the incident photon energy to the K-edge of the substituted element. Combined with theoretical calculations, we will discuss the local electronic states around the substituted element which are affected through the interaction with surrounding atoms.

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