Thesis High-Resolution Photoemission Study of Kondo Insulators ...

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52 Chapter 4. Evolution of Electronic States in the Kondo Alloy ... Intensity Yb 0.5 Lu 0.5 B 12 YbB 12 hν = 125 eV He II - He I difference AIM calculation ∆ =0.28 eV ∆ =0.21 eV 0.20 0.15 0.10 0.05 0.00 -0.05 Binding Energy (eV) Figure 4.6: Photoemission spectra of Yb0.5Lu0.5B12 and YbB12 near EF . Upper panel: Spectra taken with hν = 125 eV (dots) and broadened He II − He I difference spectra (solid curves). Middle panel: He II − He I difference spectra (dots) and fits using Mahan’s line shape (solid curves). Lower panel: Calculated spectra using the AIM convoluted with a Gaussian of FWHM 40 meV.
4.3. Results and Discussion 53 Intensity LuB 12 Yb 0.5 Lu 0.5 B 12 YbB 12 hν = 21.2 eV 80 40 0 -40 Binding Energy (meV) Figure 4.7: Upper panel: He I spectra of Yb1−xLuxB12 and YbB12. The solid curves have been obtained by convoluting the curves in the lower panel with a Gaussian. Lower panel: the assumed DOS multiplied by the Fermi distribution function. by ∆ = π � B B 0 ρ(ε)|V (ε)|2dε, where ρ(ε) is the conduction-band DOS and V (ε) is the hybridization matrix element between the f and conduction electrons [4.21]. In Yb1−xLuxB12, Lu-substitution may change two parameters of the model: (i) electron doping raises the Fermi level and thus reduces ε0 f; (ii) the recovery of the B sp band DOS ρ(ε) around EF increases ∆. With these changes in ε0 f and ∆, δ increases and hence ¯nf decreases according to Eq.(4.1), in qualitative agreement with the PES results. However, the calculations to lowest order in 1/Nf deal with only the unoccupied side of the conduction band for Yb compounds and are not influenced by the change in the conduction-band DOS below EF as observed in the He I spectra. Also, the line shape of the Kondo peak cannot be analyzed with lowest-order calculations, which necessarily give a single and hence symmetric peak below EF . In order to consider the effect of changes in the B sp band near EF on the f-electron spectra, we have calculated the 4f photoemission spectra at T = 0 K to second order in 1/Nf [4.23]. A flat DOS of 0.3 eV width is considered for the conduction band with EF
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Thesis High-Resolution Photoemissio
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ii CONTENTS 5.2 Experimental . . .
Page 6 and 7: 2 Chapter 1. Introduction Figure 1.
Page 8 and 9: 4 Chapter 1. Introduction Figure 1.
Page 10 and 11: 6 Chapter 1. Introduction peaks, wh
Page 12 and 13: 8 Chapter 1. Introduction only the
Page 14 and 15: 10 Chapter 1. Introduction directio
Page 16 and 17: 12 Chapter 1. Introduction activati
Page 18 and 19: 14 References [1.14] F. Iga, M. Kas
Page 21 and 22: Chapter 2 Photoemission Spectroscop
Page 23 and 24: 2.1. General Principles 19 Photoele
Page 25 and 26: 2.1. General Principles 21 where R(
Page 27 and 28: 2.2. Experimental 23 DOS Intensity
Page 29 and 30: 2.2. Experimental 25 Figure 2.5: Il
Page 31 and 32: 2.2. Experimental 27 baking out the
Page 33: References [2.1] O. Gunnarsson and
Page 36 and 37: 32 Chapter 3. Photoemission Study o
Page 48 and 49: 44 References the Kondo peak positi
Page 50 and 51: 46 Chapter 4. Evolution of Electron
Page 63 and 64: References [4.1] G. Aeppli and Z. F
Page 65: References 61 [4.25] P. Weibel,M. G
Page 68 and 69: 64 Chapter 5. Temperature Dependenc
Page 78 and 79: 74 References [5.10] N. Shimizu, F.
Page 81 and 82: Chapter 6 Substitution and Temperat
Page 83 and 84: 6.1. Introduction 79 Figure 6.2: Ma
Page 85 and 86: 6.3. Results and Discussion 81 6.3
Page 87 and 88: 6.3. Results and Discussion 83 DOS
Page 89 and 90: 6.3. Results and Discussion 85 dist
Page 91 and 92: 6.3. Results and Discussion 87 Apar
Page 93 and 94: 6.3. Results and Discussion 89 of E
Page 95 and 96: 6.3. Results and Discussion 91 the
Page 97: 6.4. Summary 93 and consistent anal
Page 100 and 101: 96 References [6.11] M. J. Rozenber
Page 102 and 103: 98 Chapter 7. Temperature and Co-Su
Page 104 and 105: 100 Chapter 7. Temperature and Co-S
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102 Chapter 7. Temperature and Co-S
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References [7.1] G. Aeppli and Z. F
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Chapter 8 Temperature and Al-Substi
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8.2. Experimental 113 and Fisk [8.2
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8.3. Results and Discussion 115 8.3
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8.3. Results and Discussion 117 Int
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8.3. Results and Discussion 119 dep
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8.3. Results and Discussion 121 σ
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8.4. Summary 123 temperature magnet
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126 References [8.14] T. Tonogai, A
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128 Chapter 9. Conclusion has shown
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130 Chapter 9. Conclusion (a) FeSi
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132 Chapter 9. Conclusion developed
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