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tight binding 計算によるペロブスカイト型酸化物薄膜の ARPES の解析. 和達大樹、近松彰 A 、組頭広志 A 、 吉田鉄平 B 、溝川貴司 B 、藤森淳 B 、尾嶋正治 A 東大理、東大工 A 、東大新領域 B. 科研費基盤研究 A 「単結晶薄膜化により物性を制御した強相関系遷移金属酸化物の電子構造の研究」研究会 於 東京大学 柏キャンパス 2005 年 6 月 17 日. ARPES of La 1-x Sr x FeO 3 thin films. Experimental band structure - PowerPoint PPT Presentation
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科研費基盤研究 A「単結晶薄膜化により物性を制御した強相関系遷移金属酸化物の電子構造の研究」研究会
於 東京大学 柏キャンパス 2005 年 6 月 17 日
tight binding 計算によるペロブスカイト型酸化物薄膜の ARPES の解析
和達大樹、近松彰 A 、組頭広志 A 、吉田鉄平 B 、溝川貴司 B 、藤森淳 B 、尾嶋正治 A
東大理、東大工 A 、東大新領域 B
ARPES of La1-xSrxFeO3 thin films
ARPES spectra Experimental band structure (2nd derivative plot)
• eg bands (~ -1.3 eV) : significant dispersion• t2g bands (~ -2.4 eV) : weak dispersion• O 2p bands (-4 ~ -6 eV)
Inte
nsi
ty (
arb
. u
nits
)
-10 -8 -6 -4 -2 0Energy relative to EF (eV)
h = 68 eV
=
4o
12o
24o
t2g
eg
O 2p
32o
Tight-binding band-structure calculation
PM state(SrTiO3: L. F. Mattheiss,
Phys. Rev. 181, 987 (1969).)
G-type AF state
G-type AF
0 E⑤
③
③
Basis : 14 Basis : 28
③ ③
③
③
③
③
⑤ ⑤
FeO
③
Comparison with AIPES spectra
• Three main structures of the valence-band AIPES spectrum and the crystal field splitting of the O 1s XAS spectrum were reproduced.• The satellite structure could not be reproduced.
Density of states Comparison with AIPES spectra
Optical gap of LaFeO3 : Egap = 2.1 eV(T. Arima et al., PRB 48, 17006 (1993))
p-d = 0 eV, d-d, = 0.41 eV, p-p = 0 eV,(pd) = -1.5 eV, (pp) = 0.60 eV
E = 5.3 eV
DO
S
-8 -6 -4 -2 0 2 4Energy (eV)
'DDOS(U=5.3).DAT' 'DDOS3(3)(U=5.3).DAT' 'DDOS4(4)(U=5.3).DAT' 'DOS(U=5.3).DAT' 'DDOS(1)(U=5.3).DAT' 'DDOS(2)(U=5.3).DAT'
eg
t2g
eg
t2g
EF (x = 0.4)(filling)
2.1 eV
total Fe 3d
Inte
nsity
(ar
b. u
nits
)-10 -5 0 5
Energy relative to EF (eV)
LaFeO3
ABC
Fe 3d
La 5d
tight-binding
PES XAS
sat.
DE
total Fe 3d O 2p
h = 600 eV
Expt.
• Band folding of Fe 3d eg bands could be reproduced. • Fe 3d t2g bands, O 2p bands … good agreement
Comparison with ARPES results
88 eV
X
X X
XM M
74 eVHole pockets
ARPES of La1-xSrxMnO3 thin films
ARPES spectra Experimental band structure (2nd derivative plot)
eg ↑ bands
t2g ↑ bands
Reconstruction-derived surface bands
O 2p bands
88 eV
(003) (103)
Z
X X
Z
R R
60 eV
Z R Z R
A. Chikamatsu et al. cond-mat/0503373.
Tight-binding band-structure calculation
PM state(SrTiO3: L. F. Mattheiss,
Phys. Rev. 181, 987 (1969).)
FM state
0 E⑤
③
③
Basis : 14Basis : 14
③ ③
③
③
③
③
⑤ ⑤
MnO
③
FM
Tight-binding calculation (-X direction)
p-d = -3 eV, d-d, = 0.41 eV, p-p = 0 eV,(pd) = -2.0 eV, (pp) = 0.60 eV
E = 4.6 eV
ARPES Data: A. Chikamatsu et al. cond-mat/0503373.
Reconstruction-derived surface bands
eg ↑ bands
t2g ↑ bands
O 2p bands
Strong electron correlation
Majority-spin bandsMinority-spin bands
eg↑ bands cross EF. (half-metallic behavior)
88 eV
(003) (103)
Z
X X
Z
R R
60 eV
Z R Z R
ARPES form 3-dimensional materials
kll
kll
Momentum parallel to surface
Momentum perpendicular to surface kz
z
kz
kz
kll
Simulated band structure (88 eV)
kz = 0 kz = 1/ kz = ∞
Finite escape depth kz broadening (Lorentzian function)
Comparison with high-symmetry line (-X)
88 eV (kz = 1/)vs
-Xdirection
2.52.01.51.00.50
Wave Number [Å-1
]
-10
-8
-6
-4
-2
0
2
En
erg
y re
lativ
e t
o E
F (
eV
)
h = 88 eV
The trace obtained at 88 eV
nearly
-Xdirection
Effect of kz broadening
Summary
• La1-xSrxMnO3
eg↑ bands cross EF. (half-metallic behavior) FM state
• La1-xSrxFeO3 eg↑ bands do not cross EF. (insulating behavior) G-type AF state
• The effect of kz broadening is important for the interpretation of ARPES results.
• Future work … Effect of matrix element
• In-situ photoemission measurements on single-crystal thin films of La1-xSrxFeO3 and La1-xSrxMnO3 were analyzed using tight-binding model calculation.