“ 放射光を利用した物性科学の発展と展望” 研究会原研放射光科学研究センター、 2004 年 3 月 18-19 日　

f 電子系超伝導体の軟X線放射光分光 “放射光を利用した物性科学の発展と展望” 研究会原研放射光科学研究センター、2004年3月18-19日　藤森　淳（東大新領域、原研放射光）共同研究者藤森伸一、斎藤祐児、岡根哲夫、岡本淳、中谷健、村松康司（原研放射光）間宮一敏（KEK－PF）島田賢也、成村孝正、小林賢一、生天目博文、谷口雅樹（広島大放射光）池田修悟、青木大、宍戸寛明（阪大理）芳賀芳範、山本悦嗣、松田達麿（原研先端研）大貫惇睦（阪大理、原研先端研）山上浩志、常盤欣文（京都産業大）、播磨尚朝（阪大産研）田中新（広島大先端物質）

Outline • JAERI beamline BL-23SU • PES • MCD • Ce and U exotic superconductors • Ce115 compounds: superconductivity near QCP • U115 compounds • Ferromagnetic superconductor UGe2 • Antiferromagnetic superconductor UPd2Al3

RI samples (U compounds) Beamlines in Spring-8

JAERI beamline BL-23SU of Spring-8 Y. Saitoh et al., Nucl. Instrum. Methods A ’01.

JAERI beamline BL-23SU of Spring-8 Y. Saitoh et al., Rev. Sci. Instrum. ’ 00

MCD Synchrotron Radiation PES JAERI beamline BL-23SU of Spring-8 ARPES装置 MCD装置 PES station Scienta 2002, Gammadata VUV5000 MCD station Superconducting magnet, up to 10 T Low temperature, down to 10 K U compounds can be measured

Resonant photoemission S.I. Fujimori et al

K. Shimada et al. Resonant photoemission A. Sekiyama et al., Nature ‘00.

Angle-resolved photoemission (ARPES)

MCD in core-level x-ray absorption from metal 2p core level spin sum rule Apple II-type helical undulator orbital sum rule Element-selective magnetic probe A1 - A2 Superconducting magnet, up to 10 T Low temperature, down to 10 K

Superconductivity near quantum critical point superconducting quantum critical point Doniach’s phase diagram Non-Fermi liquid Antferromagnetic metal Fermi liquid S. Doniach G.G. Lonzarich

Quasi-2D superconductors near quantum critical point CeTIn5 (T=Rh, Ir, Co) In antiferromagnetic Rh, Ir supercond. Ce Superconductivity at ambient pressure in CeIrIn5 (TC = 0.4 K) and CeCoIn5 (TC = 2.2 K) H. Hegger et al. PRL ‘00 H. Shishido et al. PRB ‘02

Quasi-2D superconductors near quantum critical point CeTIn5 (T=Rh, Ir, Co) H. Shishido et al. JPSJ 02 CeCoIn5 CeRhIn5 CeIrIn5 quantum critical point pressure Doniach’s phase diagram Non-Fermi liquid superconducting Antferromagnetic metal Fermi liquid S. Doniach G.G. Lonzarich

Resonant photoemission and XAS Ce 4d-4f @ Hi-SOR Ce 3d-4f Ce 3d XAS @ Spring-8 spin-orbit sideband nf ~ 1 S.I. Fujimori et al., PRB ‘03 S.I. Fujimori et al., Physica C ‘03

CeRhIn5: AREPS and band-structure calculations hn = 21.2 eV S.I. Fujimori et al., PRB ‘03 Band calc: H. Harima

CeIrIn5: AREPS and band-structure calculations hn = 21.2 eV S.I. Fujimori et al., PRB ‘03 Band calc: H. Harima

ARPES Fermi surfaces in CeIrIn5 Fermi surface mapping compared with LDA Fermi surface of CeIrIn5 by LDA calculation H. Harima A M S.I. Fujimori et al., PRB ‘03

Hybridized spd-f band model Wf Ce compound La compound f band spd band

Hybridized spd-Ce 4f bands in CeIrIn5 4d-4f RPES (hn = 122 eV) → Ce 4f @ Hi-SOR He I (hn = 21.2 eV) → sp S.I. Fujimori et al.

Quasi-2D UTGa5 (T = Fe, Pt) UGa3 UTGa5 U Fe, Pt Ga Ga Fe, Pt U UFeGa5 : paramagent UPtGa5 : antiferromagnet (TＮ=26K) cf) PuCoGa5: superconductor (TC=18.5K)

Photoemission spectra of UTGa5 (T = Fe, Pt) Fe 3d U 5f U 5f sensitivity PM AFM U 5f S.I. Fujimori et al.

Band structure and Fermi surfaces of UFeGa5 wide 5f band Fermi surface mapping S.I. Fujimori et al. Band calc: H. Yamagami

Photoemission spectra of UTGa5 (T = Fe, Pt) Fe 3d U 5f U 5f sensitivity PM AFM U 5f S.I. Fujimori et al.

Band structure of UPtGa5 narrow 5f band S.I. Fujimori et al.

Ferromagentic superconductor UGe2 ferromagnetic T* new order parameter ? supercond. TCurie = 52 K TSC = 0.8 K@1.2 GPa T*~ 30 K: anomaly ? TCurie T* S. S. Saxena et al., Nature ‘00 A. Huxley et al., PRB ‘01 N. Tateiwa et al., JPSJ ‘01

U M4,5 (3d 5f) MCD of U compounds US Raw data (TFY method) self-absorption effects Corrected data matrix-element effects ?? S.P. Collins et al., J. Phys. Cond. Mat. ‘95

U N4,5 (4d 5f) MCD of UGe2 mL mS mL/mS MCD (T=25K) 2.9 -1.5 -1.9 Neutron U4+ 2.37 -0.91 -2.60 diffraction U3+ 2.62 -1.17 -2.24 LDA 2.98 -1.52 -1.46 T. Okane et al. Neutron: Keranvanois et al., PRB ‘01

U N3 (4p 6d), Ge L2,3 (2p 4s)MCD of UGe2 Finite Ge L2,3 MCD Finite polarization of Ge 4s electrons No polarization of U 6d electrons T. Okane et al.

U N4,5 (4d 5f) MCD of UGe2 mL mS mL/mS MCD (T=25K) 2.9 -1.5 -1.9 Neutron U4+ 2.37 -0.91 -2.60 diffraction U3+ 2.62 -1.17 -2.24 LDA 2.98 -1.52 -1.46 T. Okane et al. Neutron: Keranvanois et al., PRB ‘01

U N4,5 MCD of UGe2 : Temperature dependence TCurie T* T. Okane et al.

Antiferromagentic superconductors UPd2Al3 UNi2Al3 UPt3 a= 5.382 Å c= 4.189 Å TN= 14K(0.85mB) TC= 2 K a = 5.027 Å c= 4.018 Å TN= 2.4K(0.24mB) TC= 1 K a= 5.764 Å c= 4.899 Å TN= 5 K(0.02mB) TC= 0.4 K U 5f electrons localized itinerant

Photoemission spectra of UPd2Al3 S.I. Fujimori et al.

Conclusions • Ce115 compounds: superconductivity near QCP • Ce 4f electrons are nearly localized, nf ~ 1. • but participates in band/Fermi surface formation in CeIrIn5. • U115 compounds • Different degrees of localization have been demonstrated between UFeGa5 and UPtGa5. • Ferromagnetic superconductor UGe2 • Spin and orbital moments and their temperature dependence have been obtained by MCD • with no anomaly at ~T* • High (optimized) beamline performance has been achieved at BL-23SU. • Many scientific opportunities are foreseen.

Scientific opportunities at BL-23SU • U compounds • SX-AREPS, MCD, core-level XPS • Basic sciences of strong correlation • 3-dimensional transition-metal oxides -- SX-ARPES • Ferromagnetic oxides -- MCD • Nano-sciences • Diluted magnetic semiconductors -- MCD at low-T, high-H • Oxide thin films, interfaces, nano-structures • Intercalation, nano-magnets, …..

PES PLD CCD Cameras SR Combined in situ PES-PLD system cf. Oshima group at KEK-PF

Scientific opportunities at BL-23SU • U compounds • SX-AREPS, MCD, core-level XPS • Basic sciences of strong correlation • 3-dimensional transition-metal oxides -- SX-ARPES • Ferromagnetic oxides -- MCD • Nano-sciences • Diluted magnetic semiconductors -- MCD at low-T, high-H • Oxide thin films, interfaces, nano-structures • Intercalation, nano-magnets, ….. • New directions: Proposals are welcome !

原研放射光・電子物性研究グループ ■研究テーマ "強相関電子系機能性材料の電子構造に関する研究"超伝導や巨大磁気抵抗など特異な物性を示す遷移金属、希土類、ウランを含む強相関電子系物質とこれらの物質を複合化、ナノ構造化した新しい機能を持つ物質・材料の化学結合状態・電子構造を各種軟x線分光法を用いて明らかにする。得られた情報から物質設計・材料設計の指針を得てIT、環境、エネルギーに関連した新材料の開発に資する。 ■メンバー安居院あかね / Akane Agui岡根哲夫 / Tetsuo Okane岡本淳 / Jun Okamoto　　博士研究員斉藤祐児 / Yuji Saitoh竹田幸治 / Yukiharu Takeda　　博士研究員竹山雅義 / Masayoshi Takeyama　業務協力員寺井恒太 / Kota Terai　　博士研究員中谷健 / Takeshi Nakatani藤森淳 / Atsushi Fujimori　　客員研究員藤森伸一 / Shinichi Fujimori村松康司 / Yasuji Muramatsu　　グループリーダー

“ 放射光を利用した物性科学の発展と展望” 研究会原研放射光科学研究センター、 2004 年 3 月 18-19 日