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gsbNX ¡ d¢dqn´`±Ì UPd2Al3 ÉÎ·éî X üúËõpxªðõdqªõ·×ÄÌ U 5f dqÍÕðIÈ¿dqÆµÄæèµíêÄ¢éBÈ¨CªèÍ20 K ÈãÅsíêÄ¢é½ß¿Íí¥«óÔÉèCohvZàí¥«óÔð¼èµÄsÁ½B

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Ngiªè·x20 KjÆCU 5f dqðÕðdqÆµÄæèµÁ½ohvZÉæé U 5f Æ Pd 4d ÌªóÔ§xð¦·B±ÌGlM[ÌæÅÍCU 5f óÔÆ Pd 4d
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Fig. 2 a, The angle integrated photoelectron spectroscopy (AIPES)
spectra measured at hn400 and 800 eV, together with thecalculated Pd 4d and U 5f density of states. b, The procedureof deriving of the experimental U 5f partial density of states.
The spectrum measured at hn400 eV (green curve) has
been subtracted from that measured at hn800 eV (redcurve). The spectrum measured at hn400 eV has beenbroadened to simulate the energy resolution of the spectrum
measured at hn800 eV. Both spectra have been normalized
so as to match the tail of Pd 4d states located within EB2_3
eV with each other. c, The obtained U 5f partial density ofstates is shown as blue solid curve and is compared with thecalculated U 5f partial DOS.

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êçÌ\¢ÍåÉ Pd 4d dqóÔÉæéñ^ÅéÆlÁÄÄ»³êÄ¢È¢±Æªª©éB±Ì±Æ©çCÈO¦çêéB±±ÅÚ·é×«_ÍCpxÏªXyNg

Ì¤ÅÍ±Ì\¢ÍÇÝ U 5f dqóÔð\·àÌÆµÉ¨¢ÄuÇÝI 5f dqvÉæé\¢ªÏª³êÄ¢éúËõ Jan. 2009 Vol.22 No.1  13

Fig. 3a, the hexagonal Brillouin zone of UPd2Al3 in a paramagnetic phase. b, The position of the ARPES scan. The red
curve represents the momentum position of ARPES cut with hn595 eV. u0corresponds to the L point and u5.4does the A point. The shaded area indicates the momentum broadening for k direction due to the nite
electron escape depth. c, The density plot of the SX­ARPES spectra measured 20 K. d, The calculated energy dis­persions to be compared with the experiment. Contribution from the U 5f and Pd 4d states in each band are also
indicated on the color scale.

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î X üpxªðõdqXyNgÌ·xÏ»³çÉCpxªðõdqªõXyNgÌ·xÏ»ÌªÄCGlM[ 1 eV tßÌoh\¢ª°È·xèðsÁ½B±Ì»¨ÍT^IÈd¢dqnÌUé¢Ï»ð¦µÄ¢éBÜ½CGlM[ 2 eV tßÌ

14  úËõ Jan. 2009 Vol.22 No.1

gsbNX ¡ d¢dqn´`±Ì UPd2Al3 ÉÎ·éî X üúËõpxªðõdqªõ

Fig. 4a, ARPES spectra of UPd2Al3 measured at 20 K and 100 K. b, ARPES spectra of UNi2Al3 measured at 20 K and
100 K. The temperature dependences were observed in UPd2Al3 while they were not in UNi2Al3.

Pd 4d óÔ©çÌñ^ª­¢ohÉÂ¢ÄÍC·É¨¢Ä»Ìs[N­xªã­ÈéÌªÏª³êÄ¢éªCãÉq×éæ¤É»Ìs[NÊuÍÏ»µÄ¢È¢B±êçÌXyNgÌ·xÏ»ª{¿IÅé©ðmF·é½ßCUPd2Al3 æèàÕðIÈ U 5f dqóÔðÂ
UNi2Al3 ÉÎ·é ARPES XyNgÌªèðsÁ½B
UNi2Al3 Í300 K ÜÅÌÍÍÅÑ¥¦ª Curie­Weiss IÈ
Ué¢ð¦µÄ¢È¢½ßCU 5f dqóÔÍñíÉÕ
ðIÅÁ«·xÍ300 K ÈãÅéÆl¦çêÄ¢é18)BÊð Fig. 4b É¦·B±Ì·xÍÍÉ¨¢ÄXyNg
Ì·xÏ»Í UNi2Al3 ÉÍÏª³êÄ¢È¢±Æªí©
éB±Ì±Æ©çCUPd2Al3 ÉÏª³êÄ¢é·xÏ»ÍCdqóÔÌ{¿IÈÏ»ð½fµÄ¢é±ÆªðÅ«éB
É±ÌXyNgÌ·xÏ»ÌÚ×ð©é½ßÉCX
yNgÌñK÷ªðæÁÄXyNgÌs[NÊuÌ±oðsÁ½BñK÷ªðæéÛÉ EF ÌJbgIt©çÌ­¢ñ^ðð¯é½ßCÜ¸GlM[ªð\ÉæéLªèðôÝñ¾ Fermi­Dirac ÖÉæÁÄXyNgðéðsÁ½BFig. 5a, b ÉGlM[ªð\ÉæéLªèðôÝñ¾ Fermi­Dirac ÖÅÁ½ ARPES Xy

Fig. 5a_b, ARPES spectra divided by the convoluted Fermi­Diracfunction. c_d, Experimental band structure derived by add­
ing the second derivatives of EDC's and MDC's in a proper
ratio. Higher intensity part corresponds to the peak positionin the ARPES spectra. The circles indicate the positions ofchanges of the band structure in higher binding energy sides.

Ngð¦·BEF tßÉÊu·é±qohÌ\¢ª¼ÒÅÙÈÁÄ¢é±Æªª©éBFig. 5c, d ÉCGl

¢Ä EF tßÅ·¢ohð`¬µÄtF~ÊÉñ^µM[ûüÉñK÷ªðæÁ½ UPd2Al3 Ìoh\¢Ì·Ä¢½±qohª·É¨¢ÄGlM[¤ÉxÏ»ð¦·B±ÌC[WÉ¨¢ÄC­xÌ­¢ªª

VtgµCtF~ÊÖÌñ^ð¸­³¹Ä¢é±Æªªs[NÊuÉÎ·éB±êçÌXyNgÉÍñíÉå

©éBÜ½C³çÉÍ EF ©çGlM[ 1 eV tß«È·xÏ»ª»êÄ¢é±Æªª©éBÜ¸Cá·É¨

ÉÊu·é\¢i}É¨¢Ä 1, 2 ÅÍñ¾ªjÌÏ»úËõ Jan. 2009 Vol.22 No.1  15àæèÍÁ«èÆÏª³êÄ¢éBêûÅCGl

5. ÜÆßÆ¡ãÌW]M[ 1 eV ÈãÌ Pd 4d óÔÌñ^ª­¢ohÉÂ¢ÄÍC»Ì­xªÏ»µÄ¢éàÌÌCohÌGlM[î X üpxªðõdqªõ@ðp¢Äd¢dqn´`ÊuÍÙÆñÇÏ»µÄ¢È¢±Æªí©éB±Ì±Æ±Ì UPd2Al3 ÌdqóÔðÏªµCoh\¢Ì±o¨

ÍC±ÌGlM[ÌæÉ¨¢ÄÍC{¿IÈoh\¢æÑ»Ì·xÏ»ÌÏªðsÁ½Bá·É¨¯éÍ·xÏ»ð½È¢±Æð¦´µÄ¢éB

UPd2Al3 Ìoh\¢ÍCU 5f dqðÕðÆµÄæèµ4.4©ÆÈèCU 5f dqÉÎµÄÍÕðIÈLqªæ¢o­Á½ohvZÉæÁÄärIæ­Lq³êé±Æª¾çl@ÈãÌÊðÜÆßéÆC20 K Åªèµ½ ARPES X_ÆÈé±Æð¦µ½BÜ½CU 5f dqóÔÍÁ«·xyNgÉÍ¾ÄÈohªUªÏª³êCU 5f dqó

T Þ`50 K tßð«É·xÏ»ð¦µCá·ÅÌÕðIÈ

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é±Æð¦µÄ¢éBßNÌõdqªõZpÌòôIÈiWÉºÁÄCêÍtF~Êð`¬µÄ¢½ U 5f dq±qohÍ·âØµÄ¢½d¢dqnÉÎ·éõdqªõÀ±ªÄÑi100 KjÉ¨¢ÄGlM[¤ÉÚ®µCtF

CðæµÄ¢éBGlM[ªð\âoNq´«ð~ÊÖÌñ^ª¸­µÄÇÝIÈ«¿ð¦·±Æª¾çpµ½¤Êª±XÆñ³êÄ¨è22_27) C¡ãà©ÉÈÁ½B±Ì»¨ÉÎ·éõw`±xªèÌÊð±Ìæ¤ÈVµ¢õdqªõÀ±ªd¢dqn¨Ì¤©éÆC·ÅÍÊíÌà®IÈ Drude s[NªÏª³ÉÎµÄå«­v£Å«é±ÆðèÁÄâÜÈ¢BêÄ¨èCtF~ÊÉÍd¢±qÍ¶ÝµÄ¢È¢àÌÌC50 K ÈºÅÍd¢±qÉNö·é¬¬MbvªÏª³êÄCtF~ÊÉñ^·é·¢ 5f ohÌ`Ó«±Ì¤ðißéãÉ¨¢ÄCLvÈc_ðµÄ¢½¾¬ª¦´³êÄ¢é19) B±êÍ¡ñÌ ARPES ÅÏª³¢½²¡º³öi¼Ã®åwjCOîa³³öiåãå

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iTechnische Universitat BraunschweigjCG. H. Lander ³lM[ 1 eV öxÌÍÍÉ

éohà·xÏ»ð¦·öiInstitute for Transuranium ElementsjÉ´ÓvµÜ±Æª¾ç©ÆÈÁ½B±Ìæ¤ÈC·xÏ»Éæé 1· B Ü ½ C ± Ì ¤  Í È w ¤  ï â  à i á è B,

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éB±êçÌd¢dqnÌî{IÈ«¿Åé·ÅÌÇÝóÔ©çá·ÅÌÕðóÔÖÌÏ»ðà¾·éÉÍCVµ¢_IÈggÝðKvÆµÄ¢é±Æð¦µÄ¢éBêûÅC³çÉGlM[¤ÉÊu·é U 5f dq©çÌñ^ªñíÉ¬³¢ohÉÂ¢Ä1)2)Í{¿IÈ·xÏ»ð¦µÄ¢È¢B±ÌGlM[ÌæÉ¨¯és[N­xÌÏ»ÍCtHmÉæéõdqÌU21)ÈÇª´öÆµÄl¦çêéB{¤ÍC·É¨¯éÇÝóÔÆá·ÅÌÕðóÔÆ

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ÄlªKvÈ±Æð¦´µÄ¢éB

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¡XLê

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18  úËõ Jan. 2009 Vol.22 No.1

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gsbNX ¡ d¢dqn´`±Ì UPd2Al3 ÉÎ·éî X üúËõpxªðõdqªõSoft X­ray angle resolved photoelectron
spectroscopy study of heavy Fermion
superconductor UPd2Al3
Shin­ichi FUJIMORI1, Yuji SAITOH1, Tetsuo OKANE1,
Atsushi FUJIMORI1,2, Hiroshi YAMAGAMI1,3, Yoshinori HAGA4,
5
Etsuji YAMAMOTO4, Yoshichika ONUKI

1Synchrotron Radiation Research Unit, Japan Atomic Energy Agency, Mikazuki, Hyogo 679_
5148, Japan
2Department of Physics, University of Tokyo, Hongo, Bunkyo­ku, Tokyo 113_0033, Japan

3Department of Physics, Faculty of Science, Kyoto Sangyo University, Kyoto 603_
8555, Japan

4Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319_
1195, Japan
5Graduate School of Science, Osaka University, Toyonaka, Osaka 560_
0043, Japan

Abstract We have performed angle­resolved photoemission experiments in soft X­ray region (SX_ARPES)
for the heavy Fermion superconductor UPd2Al3 to observe its band structure. At low temperatures (20 K),
renormalized quasi­particle bands were observed in the vicinity of the Fermi level. The overall structure of
ARPES spectra including strongly dispersive bands on the higher binding energy sides is fairly well explainedby the band structure calculation treating U 5f electrons as being itinerant. This suggests that itinerant
description is a reasonable approach to understand their electronic properties at low temperatures. On theother hand, at high temperatures (100 K), the quasi­particle bands moved toward higher binding energies,
and became less dispersive. This suggests that the U 5f electrons change their character from itinerant one at
low temperatures to localized one at high temperatures. These results give important information for the un­derstanding of the unconventional superconductivity in this compound.

úËõ Jan. 2009 Vol.22 No.1  19