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

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126 References [8.14] T. Tonogai, A. Ohno, and H. Takagi, unpublished. [8.15] T. Susaki, A. Sekiyama, K. Kobayashi, T. Mizokawa, A. Fujimori, M. Tsunekawa, T. Muro, T. Matsushita, S. Suga, H. Ishii, T. Hanyu, A. Kimura, H. Namatame, M. Taniguchi, T. Miyahara, F. Iga, M. Kasaya, and H. Harima, Phys. Rev. Lett. 77, 4269 (1996). [8.16] N. E. Bickers, D. L. Cox, and J. W. Wilkins, Phys. Rev. Lett. 54, 230 (1985). [8.17] B. C. Sales, E. C. Jones, B. C. Chakoumakos, J. A. Fernandez-Beca, H. E. Harmon, J. W. Sharp, and E. H. Volckmann, Phys. Rev. B 50, 8207 (1994).
Chapter 9 Conclusion We have studied the electronic states in Kondo insulators YbB12 and FeSi by highresolution photoemission spectroscopy (PES). The principal results are schematically illustrated in Fig. 9.1 for YbB12 and in Fig. 9.2 for FeSi. We have found that the observed position of the Kondo peak in YbB12 agrees with the Kondo temperature (TK) estimated from the magnetic susceptibility peak at T ∼ Tmax (Fig. 9.1 (a)), indicating that single-site Kondo effect indeed governs the magnetic properties in this temperature range. By introducing a model self-energy to compare the photoemission spectra with first-principle band-structure calculation, the mass renormalization is shown to be strongly energy dependent near EF . The density of states (DOS) of the B 2sp - Yb 5d- derived conduction band is depressed near EF . Lu substitution recovers the reduced conduction-band DOS, shifts the Yb 4f-derived Kondo peak towards higher binding energy (Fig. 9.1 (a)) and decreases the Yb valence. These results are consistently analyzed using the Anderson impurity model. The temperature dependence of the B sp-derived conduction band of YbB12 and Yb1−xLuxB12 has been measured with higher energy resolution. We have observed the temperature-dependent DOS which is consistent with its unusual magnetic susceptibility and electrical resistivity. A sharp dip of ∼ 10 meV width appears at low temperatures (
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Thesis High-Resolution Photoemissio
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ii CONTENTS 5.2 Experimental . . .
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2 Chapter 1. Introduction Figure 1.
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4 Chapter 1. Introduction Figure 1.
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6 Chapter 1. Introduction peaks, wh
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8 Chapter 1. Introduction only the
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10 Chapter 1. Introduction directio
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12 Chapter 1. Introduction activati
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14 References [1.14] F. Iga, M. Kas
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Chapter 2 Photoemission Spectroscop
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2.1. General Principles 19 Photoele
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2.1. General Principles 21 where R(
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2.2. Experimental 23 DOS Intensity
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2.2. Experimental 25 Figure 2.5: Il
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2.2. Experimental 27 baking out the
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References [2.1] O. Gunnarsson and
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32 Chapter 3. Photoemission Study o
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44 References the Kondo peak positi
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46 Chapter 4. Evolution of Electron
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References [4.1] G. Aeppli and Z. F
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References 61 [4.25] P. Weibel,M. G
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64 Chapter 5. Temperature Dependenc
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74 References [5.10] N. Shimizu, F.
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