Strong reduction of quasiparticle scattering rate with gap formation in CeNiSn

Abstract

We measured the temperature dependence of the surface impedance (Formula presented) at 9.6 and 14 GHz in a single crystal of the Kondo lattice compound CeNiSn, from which microwave complex conductivity (Formula presented) was determined. Below about 10 K the imaginary part (Formula presented) increases rapidly and the real part (Formula presented) is much lower than the dc conductivity. These results indicate a rapid decrease in the scattering rate of the quasiparticles, whose excitation spectrum is drastically changed with the coherence gap formation at low temperatures. © 1997 The American Physical Society.