1. 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

2. ARPES of La1-xSrxFeO3 thin films
Experimental band structure
(2nd derivative plot)
ARPES spectra
eg bands (~ -1.3 eV) : significant dispersion
t2g bands (~ -2.4 eV) : weak dispersion
O 2p bands (-4 ~ -6 eV)

3. Tight-binding band-structure calculation
G-type AF state
PM state (SrTiO3: L. F. Mattheiss, Phys. Rev. 181, 987 (1969).) ③ Fe ③ ③ O ③ ③ ③ ③ ⑤ ③ ⑤ ③ ⑤ DE
Basis : 14
Basis : 28
G-type AF

4. Comparison with AIPES spectra
Density of states
Comparison with AIPES spectra
Optical gap of LaFeO3 : Egap = 2.1 eV
(T. Arima et al., PRB 48, (1993))
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.
DE = 5.3 eV
ep-ed = 0 eV,
eds-edp, = 0.41 eV, eps-epp = 0 eV,
(pds) = -1.5 eV, (pps) = 0.60 eV

5. Comparison with ARPES results
Band folding of Fe 3d eg bands could be reproduced.
Fe 3d t2g bands, O 2p bands … good agreement

6. 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
A. Chikamatsu et al. cond-mat/

7. Tight-binding band-structure calculation
FM state
PM state (SrTiO3: L. F. Mattheiss, Phys. Rev. 181, 987 (1969).) ③ Mn ③ ③ O ③ ③ ③ ③ ⑤ ③ ⑤ ③ ⑤ DE
Basis : 14
Basis : 14 FM

8. Tight-binding calculation (G-X direction)
Strong electron correlation
eg ↑ bands
t2g ↑ bands
Reconstruction-derived surface bands
O 2p bands
Majority-spin bands
Minority-spin bands
eg↑ bands cross EF. (half-metallic behavior)
ep-ed = -3 eV,
eds-edp, = 0.41 eV, eps-epp = 0 eV,
(pds) = -2.0 eV, (pps) = 0.60 eV
DE = 4.6 eV
ARPES Data: A. Chikamatsu et al. cond-mat/

9. ARPES form 3-dimensional materialskz kz
kll
kll
Momentum parallel to surface
kll
Momentum perpendicular to surface kz z

10. Simulated band structure (88 eV)
Dkz = 0
Dkz = 1/l
Dkz = ∞
Finite escape depth l
kz broadening (Lorentzian function)

11. Comparison with high-symmetry line (G-X)
88 eV (Dkz = 1/l) vs
G-X direction
The trace obtained at 88 eV
nearly
G-X direction
Effect of kz broadening

12. Summary
In-situ photoemission measurements on single-crystal thin films of La1-xSrxFeO3 and La1-xSrxMnO3 were analyzed using tight-binding model calculation.
La1-xSrxFeO3
eg↑ bands do not cross EF. (insulating behavior)
G-type AF state
La1-xSrxMnO3
eg↑ bands cross EF. (half-metallic behavior)
FM state
The effect of kz broadening is important for the interpretation of
ARPES results.
Future work … Effect of matrix element