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

6.3. Results and Discussion 83
DOS (states/eV)
6
5
4
3
2
1
YbB 12
Yb f (× 1/20)
B p
LuB 12 B p (shifted)
0
-1.5 -1.0 -0.5 0 0.5
Energy relative to EF (eV)
Figure 6.4: Calculated Yb f and B p partial DOS of YbB12 [6.8] and B partial DOS of
LuB12 [6.9], where the f structure are located ∼ 4 eV below EF . We have shifted 0.57
eV the B p partial DOS of LuB12 to show the effect of the Yb f -Bp hybridization on
the B p DOS.
instrumental resolution. Also, as already mentioned for Fig. 5.1 and Fig. 5.2, the sample
quality was improved in the single crystals. It is common to the poly- and single- crystal
spectra that with Lu substitution the spectral weight between EF and 20 meV below
it increases while that below ∼ 30 meV decreases corresponding to the decrease in the
intensity of the − 80 meV peak.
6.3.2 Conduction Band in LuB12
Here we discuss the conduction band in the reference compound LuB12 and its temperature
dependence. The upper panel of Fig. 6.6 shows temperature-dependent He I
spectra of LuB12. The spectra have been normalized to the integrated intensity below
− 200 meV as done for the spectra of YbB12 in Chap. 5. The increase in the spectral
weight above EF in going 7 K to 300 K is obviously larger than the decrease below
EF , indicating a temperature dependence other than the effect of the Fermi-Dirac (FD)