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

More documents

Recommendations

Info

118 Chapter 8. Temperature and Al-Substitution Dependence of the ... DOS (a) (b) x = 0.00 x = 0.02 x = 0.05 x = 0.10 x = 0.30 FeSi 1-x Al x 295 K 7 K -400 -200 0 Energy relative to E F (meV) DOS x = 0.00 x = 0.02 x = 0.05 x = 0.10 x = 0.30 FeSi 1-x Al x 295 K 7 K -150 -100 -50 0 50 Energy relative to E F (meV) Figure 8.6: Temperature-dependent spectral DOS of FeSi1−xAlx (a). For each sample, T = 7 K (thick curves), 75 K, 150 K, 225 K, and 295 K from bottom. The vicinity of EF is enlarged in (b). corresponding to such quasiparticle DOS is observed in the photoemission spectra of FeSi on cooling and the DOS is monotonously decreased with lowering temperature3 . However, a broad peak develops around EF with decreasing Al concentration as shown in Fig. 8.4 (a) and (b). Here we have subtracted the x = 0.30 DOS at 7 K from the other DOS and have presented the temperature dependence of the difference DOS of each sample [Fig. 8.8 (a)] and the substitution dependence of the difference DOS at each temperature [Fig. 8.8 (b)]. Temperature dependence appears mainly from EF to ∼−100 meV in the x = 0.00, 0.02, 0.05, and 0.10 spectra. Especially, the depression of FeSi at low temperature in the vicinity of EF , which is recovered with a 3 Saitoh et al. [8.13] compared the photoemission spectra of FeSi with the DOS from the bandstructure calculation [8.3] corrected with a model self-energy and pointed out that due to a strong band narrowing the peak of the quasiparticle DOS is located just ∼ 10 meV below EF although the photoemission spectrum showed a maximum around ∼−0.3 eV.
8.3. Results and Discussion 119 depressed DOS (arb. units) 0 FeSi 1-xAl x DOS(295 K) - DOS(7 K) 0.05 0.10 0.15 x - 0 meV - 20 meV - 50 meV - 100 meV - 200 meV 0.20 0.25 0.30 Figure 8.7: Substitution-dependent depression of the spectral DOS from 295 K to 7 K at various energies. The DOS values are from Fig. 8.6, where the spectra have been normalized below − 0.4 eV. small substitution as presented in Fig. 8.4 (a), is sensitive also to a small temperature increase. No temperature dependence appears in the x = 0.30 spectra as shown in the bottom panel of Fig. 8.8 (a). On the other hand, a strong substitution dependence remains down to ∼−250 meV or further below. As already mentioned for Fig. 8.4, the substitution dependence becomes strong with increasing temperature. Such strong substitution dependence at high temperatures is not present in the spectral DOS of Yb1−xLuxB12. Note that in Fig. 8.8 the difference DOS at 150 K, 225 K, and 295 K grows in proportion to the deviation of Al content from x = 0.30. Such a smooth evolution of the DOS with substitution would also be present at lower temperatures but would be compensated with the pseudogap opening. In particular, the bottom panel of Fig. 8.8 (b) shows an apparent temperature independence of the spectral DOS below ∼−50 meV. Tonogai et al. have measured the optical reflectivity of the same samples and deduced the optical conductivity [8.14] as shown in Fig. 8.9. The overall temperature
Page 1:
Thesis High-Resolution Photoemissio
Page 4 and 5:
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 38 and 39:
Page 40 and 41:
Page 42 and 43:
Page 44 and 45:
Page 46 and 47:
Page 48 and 49:
44 References the Kondo peak positi
Page 50 and 51:
46 Chapter 4. Evolution of Electron
Page 52 and 53:
Page 54 and 55:
Page 56 and 57:
Page 58 and 59:
Page 60 and 61:
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 70 and 71:
66 Chapter 5. Temperature Dependenc
Page 72 and 73: 68 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
Page 113 and 114: References [7.1] G. Aeppli and Z. F
Page 115 and 116: Chapter 8 Temperature and Al-Substi
Page 117 and 118: 8.2. Experimental 113 and Fisk [8.2
Page 119 and 120: 8.3. Results and Discussion 115 8.3
Page 121: 8.3. Results and Discussion 117 Int
Page 125 and 126: 8.3. Results and Discussion 121 σ
Page 127: 8.4. Summary 123 temperature magnet
Page 130 and 131: 126 References [8.14] T. Tonogai, A
Page 132 and 133: 128 Chapter 9. Conclusion has shown
Page 134 and 135: 130 Chapter 9. Conclusion (a) FeSi
Page 136: 132 Chapter 9. Conclusion developed
show all

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

Create successful ePaper yourself

Delete template?

Save as template?