Pressure effects on the optical conductivity of Kondo insulators

The effects of pressure on the optical conductivity of Kondo insulators are studied in the framework of the slave-boson mean-field theory under the coherent potential approximation. A unified picture is presented for both the hole-type Kondo insulators [H. Okamura et al., Phys. Rev. B 58, R7496 (1998)] and the electron-type Kondo insulators [B. Bucher et al., Phys. Rev. Lett. 72, 522 (1994)]. The density of states of f electrons under the applied pressure and its variation with the concentration of the impurity doping are calculated self-consistently. The Kondo temperature and the optical conductivity are obtained, in agreement with the experiments qualitatively. The two contrasting pressure-dependent effects for the hole-type Kondo insulators and the electron-type Kondo insulators are also given as predictions for further observations.