119Sn-NMR investigations on superconducting Ca3Ir4Sn13: Evidence for multigap superconductivity.

We report bulk superconductivity (SC) in Ca 3 Ir 4 Sn 13 by means of 119 Sn nuclear magnetic resonance (NMR) experiments. Two classical signatures of BCS superconductivity in spin-lattice relaxation rate (1/ T 1 ), namely the Hebel–Slichter coherence peak just below the T c , and the exponential decay in the superconducting phase, are evident. The noticeable decrease of 119 Sn Knight shift below T c indicates spin-singlet superconductivity. The temperature dependence of the spin-lattice relaxation rate 119 (1/ T 1 ) is convincingly described by the multigap isotropic superconducting gap. NMR experiments do not witness any sign of enhanced spin fluctuations. [ABSTRACT FROM AUTHOR]