²⁰⁹Bi-NQR Investigation of the Non-magnetic Heavy-fermion Compound CeRhBi

Abstract

We report the results of ²⁰⁹Bi-NQR measurements on the heavy-fermion compound CeRhBi with the large electronic specific heat coefficient γ∼500 mJ/mol·K² at 2 K. From the Bi-NQR spectra, it is proved that no magnetic ordering occurs down to 0.15 K. The temperature dependence of nuclear spin–lattice relaxation rate 1⁄T₁ clearly demonstrates a crossover from a localized regime at high temperature to an itinerant ground state with the Kondo temperature T_K of about 8 K. It is, therefore, revealed that CeRhBi is a typical heavy-fermion compound with a non-magnetic ground state, closely located at a quantum critical point. In the context of CeRhPn (Pn = Bi, Sb, As) series, where all compounds crystallize in the same orthorhombic ε-TiNiSi-type structure, no trace of gap formation is observed in 1⁄T₁ down to 0.2 K in CeRhBi, although the values of 1⁄T₁ in the Kondo semiconductors CeRhSb and CeRhAs markedly decrease at low temperatures due to the presence of excitation gap.