Microscopic measurements in 139La-NQR of the ternary carbide superconductor LaNiC2☆

摘要: 139La-NQR measurements have been carried out in the ternary carbide superconductor LaNiC2. The nuclear quadrupole frequency and asymmetry parameter of 139La LaNiC2 were estimated to be about 1.9 MHz 0, respectively. In normal state, spin relaxation rate (1T1) NQR signal was proportional temperature (T) zero external field above superconducting transition (Tc) or an larger than critical field, which means system is Fermi-liquid state. on other hand, 1T1 decreases no more linearly with T, but rapidly exponentially as exp (−ΔkBT) at low T appreciable enhancement just below Tc. value energy gap, 2Δ, 3.34kBTc, compared 3.52kBTc BCS-value. This result strongly suggests that superconductivity a conventional BCS type.