Low-Energy Excitation in Kondo Semiconductors CeNiSn and CeRhSb

Abstract

Low-energy excitation in Kondo semiconductors CeNiSn and CeRhSb, has been investigated by the measurement of 119 Sn and 123 Sb nuclear spin-lattice relaxation rate, 1/ T 1 . From a T 3 -like temperature dependence of 1/ T 1 for both compounds, it has been intuitively concluded that the pseudo energy gap with the V - shaped structure is formed in the effective density of states for heavy quasi-particles. The band width of D =210 K and the pseudo energy gap of Δ=28 K in CeRhSb are almost two times larger than those of CeNiSn ( D =140 K and Δ=14 K), respectively. Below 0.4 K and 0.8 K for CeNiSn and CeRhSb, respectively, the T 1 T = const . behavior has been commonly observed in the two compounds, indicative of the presence of a residual density of states at the Fermi level. Impurities and/or imperfection in the samples easily mask the intrinsic V - shaped structure of the energy gap at very low temperatures.