Co L₃-edge Resonant Inelastic X-ray Scattering Study of Electronic Structures in La₁.₃Sr₀.₇CoO₄
Jun Okamoto1*, Zhi-Ying Chen2, Wen-Bin Wu1, Takao Sasagawa3, Chien-Te Chen1, Di-Jing Huang1,2
1National Synchrotron Radiation Research Center, Hsinchu, Taiwan
2Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
3Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
* presenting author:Jun Okamoto,
In high-TC cuprate La2-xSrxCuO4 system, superconductivity emerges when charge carriers are added to antiferromagnetically ordered CuO2 layers.[1] Although the carrier destroy the antiferromagnetic ordering, spin fluctuations are closely linked to superconductivity. The relationship with charge carrier and spin fluctuation is explained by charge and spin stripes in CuO2 layers.[2] La2-xSrxCoO4 system takes the same crystal structure of high-TC "214" cuprate. La2-xSrxCoO4 system is also reported to show complicated charge- and spin-ordering phase in CoO2 layers; Diagonal charge and spin stripe orders in the range of 0.3 ≦ x < 0.5 [3] and checker-board type charge-ordering around x = 0.5.[4] Their complicated ordering phases are widely studied, but, relationship of charge and spin ordering and the underlying Co 3d electronic structures are still controversy.
We have studied the low-energy excitations and the Co 3d electronic structures in La1.3Sr0.7CoO4 by measuring resonant inelastic X-ray scattering at the Co L3 edge. We discuss the observed energy-loss spectra in this presentation.

[1] P. A. Lee et al., Rev. Mod. Phys. 78, 17 (2006).
[2] J. M. Tranquada et al., Nature 375, 561 (1995).
[3] M. Cwik et al., Phys. Rev. Lett. 102, 057201 (2009).
[4] I. A. Zaliznyak et al., Phys. Rev. Lett. 85, 4353 (2000).

Keywords: strongly correlated electron systems, Resonant Inelasitc X-ray Scattering, Cobaltates