Pressure dependence of the electronic structure of 4f and 3d electron systems studied by X-ray emission spectroscopy

ABSTRACT

Techniques based on X-ray emission spectroscopy (XES) have been utilized to investigate pressure-induced changes in the electronic structure in samples subject to high pressure in the diamond anvil cell. High-resolution X-ray absorption spectra can be obtained with partial fluorescence yield mode (PFY-XAS) measurement. As typical examples, we show results of measurements of the valence fluctuating $4f$ systems of CeCu${}_2$Ge${}_2$, Ce115 systems, and YbNiGe${}_3$. The pre-edge feature of the XAS spectra at K-absorption edge of 3d-elements correlates to the spin states. We also show the results of the Fe $K\beta$ XES and PFY-XAS of K${}_x$Fe${}_{2-y}$Se${}_2$, which has two pressure-induced superconducting (SC) domes.

KEYWORDS:

• Partial fluorescence yield
• X-ray emission spectroscopy
• heavy fermion
• valence fluctuation
• superconductor

Acknowledgments

The experiments shown here were performed at Taiwan beam line BL12XU and BL12B1 at SPring-8 under SPring-8 Proposals No. 2011B4259, No. 2012A4259, No. 2012A4266, No. 2012B4253, No. 2013A4250, No. 2013A4254, No. 2014A4257, No. 2013B4127, No. 2013B4128, No. 2013B4256, No. 2013B4258, No. 2014A4256, & No. 2014A4257 (corresponding NSRRC Proposal No. 2010-3-011, No. 2012-1-013, No. 2012-1-017, No. 2012-3-011, No. 2013-3-007, & No. 2013-3-008). HY appreciates Jun'ichiro Mizuki, Yoshiya Yamamoto, Hitoshi Sato, Naohito Tsujii, Naoki Ishimatsu, Jean Pascal Rueff, and Jung-Fu Lin for reading of the manuscript and suggestions.

Disclosure statement

No potential conflict of interest was reported by the author.

Notes on contributor

Hitoshi Yamaoka graduated Hokkaido University, Japan, in 1982 and received Ph.D. in Physics at Nagoya University in 1988. Since 1992 he is a researcher in RIKEN and joined SPring-8 project. He is a senior researcher of RIKEN from 1996 and now a user of the synchrotron radiation facilities. He also occupies visiting professor positions at Kwansei-Gakuin University and Doshisha University in Japan.

Additional information

Funding

This work was partly supported by Grant in Aid for Scientific Researches (Kiban C, 15K05194) from the Japan Society for the Promotion of Science in Japan.