Indirect and direct energy gaps in the Kondo semiconductor YbB12

H. Okamura, T. Michizawa, T. Nanba +3

Optical conductivity [$\sigma (\omega )$] of the Kondo semiconductor YbB${}_{12}$ has been measured over wide ranges of temperature ($T$=8$-$690 K) and photon energy ($\hslash \omega \ge$ 1.3 meV). The…