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

Abstract

We report bulk superconductivity (SC) in Ca3Ir4Sn13 by means of 119 Sn nuclear magnetic resonance (NMR) experiments. Two classical signatures of BCS superconductivity in spin-lattice relaxation rate (1/T1), namely the Hebel-Slichter coherence peak just below the Tc and the exponential decay in the superconducting phase, are evident. The noticeable decrease of 119 Sn Knight shift below Tc indicates spin-singlet superconductivity. The temperature dependence of the spin-lattice relaxation rate (1/T1) is convincingly described by the multigap isotropic superconducting gap. Present NMR experiments do not witness any sign of enhanced spin fluctuations in the normal state.

Possible unconventional pairing in $(\text{Ca,Sr})_{3}(\text{Ir,Rh})_{4}\text{Sn}_{13}$ superconductors revealed by controlling disorder

“…While µSR measurements of both Ca 3 Ir 4 Sn 13 [58] and Sr 3 Ir 4 Sn 13 [56] agree with a single s−wave gap, they also could not rule out possible two-gap superconductivity with two very different gaps on different Fermi surface sheets. The same group discusses multi-band physics from NMR measurements [59]. The possible importance of multi-band effects was further pointed out in an electronic band-structure study where at least four sheets of the Fermi surface in Sr 3 Ir 4 Sn 13 with sizes differing by a factor of nearly 20 were found [60].…”

Second-order structural transition in the superconductorLa3Co4Sn13

“…In the Sr 3 Ir 4 Sn 13 and Sr 3 Rh 4 Sn 13 systems, the superconducting gap function is nodeless [15][16][17][18][19][20][21] and hence the superconductivity is of the conventional s-wave type. In the vicinity of the putative structural quantum critical point where T * extrapolates to 0 K, μSR [22] and specific heat [5] detected a strongly enhanced electron-phonon coupling strength, indicated by the enhancement in 2 (0)/k B T c and C/γ T c beyond the BCS weak-coupling values [35][36][37], where (0) is the size of the gap, C is the specific heat jump at T c and γ is the Sommerfeld coefficient.…”

Strong Coupling Superconductivity in the Vicinity of the Structural Quantum Critical Point in(CaxSr1−x)Yu1, Cheung2, Saines3 et al. 2015Phys. Rev. Lett.12691490View full textAdd to dashboardCite

“…A large family of superconducting stannides [16,17] with composition A 3 T 4 Sn 13 , where A=La,Sr,Ca and T=Rh,Ir, has recently attracted considerable attention [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. T c in these compounds are typically less than 10 K, and the superconducting gap function is established to be nodeless at the Fermi surface [19][20][21][22].…”