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Fig. 4

ÅInfrared reectance spectra of YbS at room temperature8).
(a) was measured in vacuum. (b) was measured in DAC at alow pressure of 0.3 GPa. (c) is an expected spectrum in
DAC, which was derived with the Kramers­Kronig analysisof the spectrum (a) measured up to 30 eV. (d) is also an ex­pected spectrum in DAC, but with the internal reectioneect, illustrated in the inset, taken into account.

Fig. 5(a) Reectance spectra of YbS measured at high pressure
and room temperature8). The missing portion of the spectra
between 0.2 and 0.3 eV could not be measured due to strong
absorption of the diamond. (b) Drude­Lorentz tting of thespectra shown in (a). See text for more detailed informa­tion.

Fig. 6(a) Optical conductivity of YbS under high pressure, derived
from the Drude­Lorentz tting of the measured reectance8).
The spectrum in vacuum was derived with Kramers­Kronig
analysis. (b) and (c) show an example of the tting at 15
GPa.

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ÅÌ R(v) ðh[fÉ[ciDLjtBbeBOµ½Êð Fig. 5(b)É¦·BFig. 5(a)ÌÀªf[^Æä×éÆCSÊIÈ R(v) Ì³ÍÏ»ðæ­Ä»Å«Ä¢é±Æªí©éBmÈ¨ Fig. 5(b)ÌtBbeBOÅÍCFig.
4 ÅGê½½d½ËÌe¿àl¶³êÄ¢éBnÉ Fig. 5(b)ÌtBbeBO©ç¾çê½p[^ÉîÃ¢Ä

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0.2, 0.7 eV t ß É 2 Â Ì ­ ¢ z û s [ N ª ¬ · µ Ä ¢tBbeBOÌáà Fig. 6(b), (c)É¦·BFig. 6(a)æ

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306  úËõ Nov. 2011 Vol.24 No.6

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éB±Ìæ¤É½Ï¿ª®l©ç¸êé»ÛÍ¿h®â¬¿ÆÄÎêÄ¢éB±êÜÅ½­Ì¿h® Yb »¨ÉÂ¢ÄC»Ì s(v) XyNgÉ0.1_0.2
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Íñ0.25 eV ÅèCÇ­mçê½¿h® Yb »¨Åé YbAl3 â YbCu2Si2 É¨¯é MIR s[NGlM[
Fig. 7Illustration for the electronic structures of YbS at high pres­sure8). The origin corresponds to the X point in the Brillouinzone, and the right edge to the G point. See the main text for
details.

Éß¢32.34) B±êçÌÊæèC³ÅÌ¿h® YbS
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Reectance [R(v)] and optical conductivity (s) of CeRu4
Sb12 at external pressure of 0 and 8 GPa and at three dierent
temperatures11). The vertical arrows indicate the positions of
mid_IR peak and their shift with pressure.

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 ÒÐî ªºpê_Ëåwåw@w¤È¨wêUÉy³ö
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jp/`infrared/êåFÔOªõC­Ödq¨«C³Èwmªðn
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2000NæèPxõÈw¤Z^[O¤õ±BïgFv_Ëåwåw@w¤È¨wêUÉ¼_³ö
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Ä2010Næè»EB

310  úËõ Nov. 2011 Vol.24 No.6

Xe¾Y

PxõÈw¤Z^[p¤£iåÉå²¤õE­mail: moriwakispring8.or.jpêåFÔOªõmªðn
1993Ns§åww¤È»wê
UmÛöC¹Cmiw)Bú{wpU»ïÁÊ¤õCÈwZpU»ÆcíªIîb¤iÆ¤õÈÇð
oÄ2000Næè»EBr{[ÀPxõÈw¤Z^[p¤£iåÉå²¤õE­mail: ikemotospring8.or.jpêåFÔOªõmªðn
1998Nkåwåw@w¤È¨wêUmÛöC¹Cmiw)BÈ
wZpU»ÆcíªIîb¤iÆ¤õðoÄ2001Næè»EBðà ¡ ³ºÌÔOªõÉæéóyÞ»¨ÌdqóÔ¤Infrared study of strongly correlated electron
systems under high pressure
Hidekazu OKAMURA
Takao NANBA
Masaharu MATSUNAMI
Taro MORIWAKIYuka IKEMOTO

Graduate School of Science, Kobe University, Kobe 657_8501, Japan
Graduate School of Science, Kobe University, Kobe 657_8501, JapanUVSOR Facility, InstitutEFor Molecular Science,
Okazaki 444_8585, Japan
Japan Synchrotron Radiation Research Institute and SPring­8,
Sayo 679_5198, Japan
Japan Synchrotron Radiation Research Institute and SPring­8,
Sayo 679_5198, Japan

Abstract Many materials exhibit interesting physical phenomena under high pressure. However, spec­
troscopic studies of materials under high pressure have not been well explored due to the technical diculties
of such experiments. Here we describe our infrared studies of strongly correlated rare earth compounds underhigh pressure using the highly bright infrared synchrotron radiation from SPring­8.

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