Conventional isotropic s -wave superconductivity with strong electron-phonon coupling in Sc5Rh6Sn18

Abstract

Sc 5 Rh 6 Sn 18 is a diamagnetic metallic compound (space group: I4 1 /acd, a ≈ 13.5 Å, c ≈ 27.1 Å) which becomes superconducting (sc) at T c = 5.15 K. The sc state was studied on single-crystal samples by temperatureand field-dependent electrical resistivity, specific heat, and muon-spin rotation (μSR) spectroscopy. No anisotropy of the upper critical field B c2 = 7.75 T is observed. Analyses of specific heat indicate enhanced values of the jump [ c p /(γ tot T c ) = 1.58] and of the energy gap ratio [ (0)/(k B T c ) = 2.39] as well as an exponential decrease of the electronic contribution below T c /2. Together with the saturation of the superfluid density for T < 3 K observed by μSR spectroscopy these findings lead us to classify Sc 5 Rh 6 Sn 18 as a moderately strong coupled isotropic s-wave superconductor. However, above T c , the crystals reveal a surprisingly anisotropic and large resistivity of 2.5-4.5 m m with metalliclike behavior perpendicular to the c axis and by a factor of ∼2 larger parallel to c, which decreases upon increasing temperature. These observations are discussed in connection to a characteristic intrinsic disorder in the crystal structure of Sc 5 Rh 6 Sn 18 .

Crystal structure, chemical bonding, and electrical and thermal transport in Sc5Rh6Sn18

“…On the other hand the local disorder could support such a scenario. This prompted us to perform an additional study of SC properties of Sc 5 Rh 6 Sn 18 , which revealed it to be a conventional SC with stronger electron-phonon coupling and isotropic s-wave gap 41 .…”

“…8). It increases with increasing temperature in the direction parallel to ab and almost linearly decreases for ρ c. Such a temperature dependence of ρ(T) could be ascribed to the strong structural disorder and low charge carrier concentration observed in Sc 5 Rh 6 Sn 18 (for more details see discussion in 41 )…”

Composition dependent polymorphism and superconductivity in Y3+x{Rh,Ir}4Ge13−x

“…It should be also pointed out that a "semiconductor"-like behavior of ρ(T ) for the non-magnetic germanides and stannides crystallizing with Remeika-like structural arrangement is frequently observed. For instance this is the case for Y 3 Ru 4 Ge 13 , [55][56][57] Lu 3 Rh 4 Ge 13 , 25 Th 3 Ir 4 Ge 13 , 21 Sc 5 Rh 6 Sn 18 58,59 etc. However, such a phenomenon is less clear now.…”

Nodeless superconductivity in Lu5−xRh6Sn18+x with broken time reversal symmetry

“…In this context, it is of particular interest to examine the superconductivity of weakly correlated centrosymmetric superconductors exhibiting TRS breaking. One such family of superconductors are the caged compounds R 5 Rh 6 Sn 18 (R = Sc, Y, Lu), which crystallize with the tetragonal space group I4 1 /acd [23], and evidence for TRS breaking is found from muon spin relaxation (μSR) measurements [24][25][26] (although TRS breaking signatures were not observed in another study for R = Sc [27]). Resistivity measurements of all three compounds show semiconducting behavior in the normal state, before becoming superconducting below 5.0, 3.0, and 4.0 K for R = Sc, Y, and Lu, respectively [28,29].…”