Multigap superconductivity in the filled-skutterudite compound LaRu4As12 probed by muon spin rotation

Abstract

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Superconducting Gap Structure of Filled Skutterudite LaOs4As12 Compound through μSR Investigations

“…A two-gap s+s-wave model of multiband superconductivity has been shown to be compatible with the temperature dependence of magnetic penetration depth of LaRu 4 As 12 . The higher gap to T C ratio computed in the s + s-wave scenario, 2∆ 1 (0)/k B T C = 3.73, is fairly comparable to the value of 3.53 for BCS superconductor in case of LaRu 4 As 12 [23]. For LaRu 4 As 12 , 2 K specific phonon modes exhibit modest softening when compared to 20 K, demonstrating that the electron-phonon interactions causing the superconductivity have an audible impact on the vibrational eigenstates [23].…”

“…The higher gap to T C ratio computed in the s + s-wave scenario, 2∆ 1 (0)/k B T C = 3.73, is fairly comparable to the value of 3.53 for BCS superconductor in case of LaRu 4 As 12 [23]. For LaRu 4 As 12 , 2 K specific phonon modes exhibit modest softening when compared to 20 K, demonstrating that the electron-phonon interactions causing the superconductivity have an audible impact on the vibrational eigenstates [23]. Using McMillan's relation, it is also possible to determine the electronphonon coupling constant (λ e−ph ) [40]:…”

“…References [24,41,42] include a description of the computations in detail. The calculated values of λ L (0) = 240 nm, n s = 8.6 × 10 27 carriers m −3 and m * = 1.749 m e for LaRu 4 As 12 [23]. The fitted parameters for LaOs 4 As 12 and LaRu 4 As 12 (for comparison) are shown in Table 1.…”

“…We recently reported unambiguous evidence of multiband s + s-wave superconductivity in LaRu 4 As 12 using muon-spin rotation measurements, with 2∆ 1 /k B T C = 3.73 for the larger gap and 2∆ 2 /k B T C = 0.144 for the smaller gap [23]. Furthermore, inelastic X-ray scattering experiments indicated essentially temperature-independent phonon modes between 300 K and 20 K, with the exception of 2 K, where a weak softening of the specific phonon modes is detected [23]. All of these results demonstrate the relevance of the electron-phonon interaction in the superconductivity of LaRu 4 As 12 , and they accord well with the DFT-based phonon simulations [24].…”

“…While the majority of La-based filled skutterudites are completely gapped superconductors, past research has shown numerous unique aspects of LaRu 4 As 12 , such as a positive curvature of H c2 , nonexponential behavior of the electronic heat capacity, and square root field dependency of the Sommerfeld coefficient (γ) [22]. We recently reported unambiguous evidence of multiband s + s-wave superconductivity in LaRu 4 As 12 using muon-spin rotation measurements, with 2∆ 1 /k B T C = 3.73 for the larger gap and 2∆ 2 /k B T C = 0.144 for the smaller gap [23]. Furthermore, inelastic X-ray scattering experiments indicated essentially temperature-independent phonon modes between 300 K and 20 K, with the exception of 2 K, where a weak softening of the specific phonon modes is detected [23].…”