ibs svo yamagata [互換モード] - dept. of phys....
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研究科紹介京都大学大学院 人間・環境学研究科
自然科学系 (物理系、化学系、地学系、生物系)大学院入試 年2回(9月、2月)
総合人間学部 人間・環境学研究科
共生人間学専攻
共生文明学専攻
相関環境学専攻
自然と人間の共生
鉄系超伝導体の元素置換効果
Ba(Fe1-xTx)2As2T= Co, Ni, CuS. Ideta, T. Y. et al., Phys. Rev. Lett. 110, 107007 (2013).T= Zn S. Ideta, T. Y. et al., Phys. Rev. B 87, 201110(R) (2013).T= MnH. Suzuki, T. Y. et al., Phys. Rev. B 88, 100501(R) (2013).
Photoemission, XASS. Ideta, H. Suzuki, I. Nishi, G. Shibata, K. Ishigami, T. Kadono, A. Fujimori,T. Shimojima, K. Ishizaka,
University of TokyoW. Malaeb, S. Shin* (ISSP)M. Hashimoto, D. H. Lu, Z.-X. Shen, Stanford UniversityE. Sakai, Y. Kotani, H. Kumigashira, K. Ono KEK-PFH. Anzai, Y. Nakashima, M. Arita, A. Ino*, H. Namatame, M. Taniguchi Hiroshima U, HiSORSamplesS. Kasahara, T. Shibauchi, T. Terashima, Y. Matsuda Kyoto UM. Nakajima, S. Uchida University of TokyoH. Eisaki, K. Kihou, A. Iyo, T. Ito, C. H. Lee, Y. Tomioka
AISTY. Nakashima, S. Yamaichi, M. Matsuo, T. Sasagawa
Tokyo Institute of TechnologyTheoryR. Arita (University of Tokyo) H. Ikeda (Kyoto U)
Collaborators
C. H. Lee et al., JPSJ (2008).
E. Pavarini et al., PRL (2001).
K. Kuroki et al., PRB (2009).
銅酸化物と鉄系超伝導体
銅酸化物 鉄系超伝導体
金属金属金属
モット絶縁体(反強磁性)
金属(反強磁性)
超伝導超伝導
超伝導
擬ギャップ
ホール量電子量 ホール量電子量
CuO2面
CuO2面
CuO2面
FeAs面
FeAs面
銅酸化物と鉄系超伝導体: バンド分散、フェルミ面
H. Shishido et al, PRL ’10.
K. Kuroki et al., PRL ‘08
H. Sakakibara et al., PRL ‘09
Cuprates
holeelectron
Single bandMulti band
スピン揺らぎを媒介とした超伝導
Theoretical prediction of line-node in SC gap
Kuroki et al., PRB ’09.
秩序パラメータの符号反転
不純物置換に弱い超伝導
hole
electron
hole hole
electron electron
hole
electron electron electron
Re (q)
I. Mazin et al., PRL ‘08Fe
PnZ
Pnictogen height Z
Transition metal substitution in BaFe2As2
Fe Co e-
Fe Ni2e-
Ba(Fe1-xTx)2As2 (T = Co, Ni, Cu, Zn)
x 2x 3x
Fe Cu 3e-
Are doped electrons working as carriers ?
Extra electronsper Fe/TM site
Electron doping Hole doping
Fe Zn4e-
4x
Experimental condition of ARPESPhoton Factory (PF) BL-28A
•Photon energy h = 33-50 eV•Measuring temperature T= 9, 35 K•Scienta analyzer SES-2002•Energy resolution ~7-10 meV•Angular resolution ~0.2º
PF BL-28A
HiSOR BL-9A
•Photon energy h = 10-34 eV•Measuring temperature T= 9, 35 K•Scienta analyzer SES-R4000•Energy resolution ~6-9 meV•Angular resolution ~0.2º
HiSOR BL-9A
Tc and TN of T-Ba122
Canfield et al., PRB ‘09.Ni et al., PRB ‘10.
Ba(Fe1-xTx)2As2 (T = Co, Ni, Cu)
Are doped electrons working as carriers ?
Band structure calculation (Supercell)
H. Wadati et al., PRL ’10. S. Konbu et al., JPSJ ’11.
Rigid-band model ?Doped electrons are localized ?
Carrier number estimated from FS volume
Part of the doped electrons do not contribute to the formation of FSs.
S. Ideta, T. Y. et al., PRL ‘13.
nh: hole carriernel: electron carrier
Tc and TN plotted as a function of nel -nh
Phase diagrams for different transition metalsubstitution accord with each other. S. Ideta, T. Y. et al., PRL ‘13.
Valence‐band spectra of Zn‐Ba122
H. Wadati et al., PRL ‘11.
TN~140 K
Zn 3d level~ 10 eV below EF
Ba(Fe1-xZnx)2As2
S. Ideta, T. Y. et al., PRB ‘13.
Fermi surface and band dispersions of Zn‐Ba122
Folded FSs and band dispersions have been observed. S. Ideta, T. Y. et al., PRB ‘13.
Fermi surface in the k//‐kz plane
Shapes of the FSs for different doping level are nearly the same.
x=0.08 x=0.25
S. Ideta, T. Y. et al., PRB ‘13.
Density of states for T‐Ba122
Total electronnumber
6 6+x 6+4x
10(1-x)1010
10x
S. Ideta, T. Y. et al., PRB ‘13.
Phase diagram of Mn-122Ba(Fe1-xMnx)2As2
M.G. Kim et al. PRB 83 054514 (2011)
A. Thaler et al. PRB 84 144528 (2011)
x<0.74
x>0.74
Partial Density of States of Mn3d orbitals
Mn PDOS is distributedaround EB=2~12eV
Inte
nsity
(arb
. uni
ts)
H. Suzuki, T. Y. et al., PRB ‘13.
Partial density of states
Emergence of local magnetic moments due to on-site Coulomb potential U and Hund coupling J
H. Suzuki, T. Y. et al., PRB ‘13.
H. Ding et al., EPL ‘08
s-波的超伝導ギャップ
s-wave-like full gap superconductivity?
s++ ?s+- ?
Ba1-xKxFe2As2 x=0.4
Superconducting gap in iron pnictide superconductorss-wave-like full gap
H. Ding et al.,EPL ’08
Octed line node
K. Okazaki et al.,Science ’12
KFe2As2(Ba,K)Fe2As2
Tc~ 4K
Tc~ 37K
等原子価置換 BaFe2(As1-xPx)2
S.Kasahara et al., PRB ‘10.
•Number of Fe 3d electronis constant.
•Pnictogen height hPndecreases.
BaFe2As2 BaFe2P2
H. Shishido et al, PRL ’10.
Phase diagram of BaFe2(As1-xPx)2
T. Yoshida et al., PRL ‘11
BaFe2(As1-xPx)2
K. Suzuki et al., JPSJ ‘11
鉄系超伝導体の超伝導ギャップ水平ノード@ホールフェルミ面
I. Mazin et al., PRB ‘10
ループノード@電子面
運動量空間のどこにノードが存在する?
ほとんどの物質ではs-波BaFe2(As,P)2などはノード(節)の存在が示唆されている。
超伝導秩序変数
ホール面
電子面
ノード
SC gap of BaFe2(As1-xPx)2 in the hole FSs
T. Shimojima et al., Science `11.
Laser ARPES
Horizontal node is unlikely ?
SC gap of BaFe2(As1-xPx)2
K. Suzuki et al., JPSJ ‘11
Y. Zhang et al.,Nature Physics `12.
Horizontal node ?x= 0.30
Isotropic gap in the electron FSs
Superconducting gap for hole FSs around the Z point
Pseudogap (cf. S. Kasahara et al., Nature ‘12.)
h= 35eVIn
tens
ity (a
rb. u
nits
)
Clear gap at low T x= 0.30, Tc=30 K
Inplane anisotropy for hole FS
h= 35eV
Inte
nsity
(arb
. uni
ts)
Symmetrized EDCs Superconducting peak Gap anisotropy
Isotropic SC gap coexists with pseudogap
x= 0.30, Tc=30 K
Spin fluctuation mechanismTheoretical prediction of line-node in SC gap
Kuroki et al., PRB ’09.
Absence of xy FS
Node in SC gap
Spin fluctuation mechanism
Three hole FSs are observed.
Orbital fluctuationsSC order parameter determined by ARPES Loop node in the electron FS
Hole FSs
Electron FSs
Saito, Onari, Kontani et al., PRB 13
Summary (Iron-based superconductor)
We have performed an ARPES study of the iron pnictide superconductors.
• Impurity effects in Ba(Fe1-xTx)2As2
Deviation from rigid-band model
• Nodal superconductivityin BaFe2(As1-xPx)2
Loop-like node in the electron FS ?
Orbital fluctuation is required to explain the observed gap anisotropy.
強相関電子系SrVO3の自己エネルギー
S. Aizaki et al., Phys. Rev. Lett. 109, 056401 (2012).
共同研究者
相崎真一,滝沢優, 出田真一郎,藤森淳 東大理
吉松公平,蓑原誠人,堀場弘司*,尾嶋正治* 東大工
K. Gupta, P. Mahadevan S. N. Bose研究所
組頭広志* 高エネ研PF
Electronic structure of SrVO3dHvA
SrVO3 ( d1)
kx
kykz
dxy
dyz
dzxI. H. Inoue et al., PRL ‘02.
T. Yoshida et al., PRB ’10.
M. Takizawa et al.,PRB ’09.
T. Yoshida et al., PRB ’10.
ARPES Bulk SVO Thin film SVO
IncoherentCoherent
Energy relative to EF (eV)
Self-energy of strongly correlated system
M. Takizawa et al.,PRB ’09.
ARPES DMFT Phenomenological model of self-energy
Extraction of the self-energy from experimental data.
「強相関電子論の基礎」藤森淳
Sample :SrVO3 / SrTiO3 (001)
Analyzer :SCIENTA SES-2002
Photon Energy :h = 50-110 eV
Temperature :T ~ 15 K
Resolution :Eres ~ 15 meV
Pressure :better than 10-10 Torr
Photon Factory BL-28A
Synchrotron radiation
Laser MBE Chamber
PhotoemissionChamber
PreparationChamber
Sample Entry
K. Horiba et al., Rev. Sci. Instrum. 74, 3406 (2003).
Sample and Experimental conditions
Band dispersions and self-energies near EF
Kink ~ 60meVElectron-phonon coupling
cf. High-Tc cuprates
QP band dispersion Self-energy
Re
One can not determinethe self-energyin the high-energy region.
Self-energy deduced from the ARPES spectra
Kramers-Kronig(KK) relation
ReG(k, )
),(1),(
kkG
k
ARPES spectra A(k,) = - ImG(k, )/
),(1),(Im),(Re
kG
kikk
),(Re),(Re),(Im),(Im
kk
kk),( knew
Electron-hole symmetry
Initial data of A(k,)
start
•k=kFA(k,)=I()+I(-)
•k<kFA(k,)=I() ()
=0 ()
Self-energy deduced from the ARPES spectra Self energy (average)
LDA+DMFT
Nekrasov et al.,PRB ’06.
A(k,)
Re
Imk=0
k=kF
k=0
k=kF
Simulation of the spectral weight A(k,w)of SrVO3
k
ARPES data
Simulation of A(k,)
Bare dispersion khas been obtained.
The QP dispersions and the incoherent part are successfully reproduced by the simulation.
)0,(1RekGk
Pole and zero surfaces of the Green function
2D Hubbard model
ReG(k,)
n nnnn
n iia 11)(
Self energy from ARPESEnergy scale of Green function
k=0
S. Sakai, Y. Motome, M. Imada, PRL ‘09.
Pole (QP)Zero(ReG=0)
zero
polepole