Possible unconventional pairing in (Ca,Sr)3(Ir,Rh)4Sn13 superconductors revea

Abstract

We study the evolution of temperature-dependent resistivity with added pointlike disorder induced by 2.5 MeV electron irradiation in stoichiometric compositions of the "3-4-13" stannides, (Ca,Sr) 3 (Ir,Rh) 4 Sn 13 . Three of these cubic compounds exhibit a proposed microscopic coexistence of charge density wave (CDW) order and superconductivity (SC), while Ca 3 Rh 4 Sn 13 does not develop CDW order. As expected, the CDW transition temperature T CDW is universally suppressed by irradiation in all three compositions. The superconducting transition temperature, T c , behaves in a more complex manner. In Sr 3 Rh 4 Sn 13 , it increases initially in a way consistent with a direct competition of CDW and SC, but quickly saturates at higher irradiation doses. In the other three compounds, T c is monotonically suppressed by irradiation. The strongest suppression is found in Ca 3 Rh 4 Sn 13 , which does not have CDW order. We further examine this composition by measuring the London penetration depth λ(T ), from which we derive the superfluid density. The result unambiguously points to a weak-coupling, full single gap, isotropic superconducting state. Therefore we must explain two seemingly incompatible experimental observations: a single isotropic superconducting gap and a significant suppression of T c by nonmagnetic disorder. We conduct a quantitative theoretical analysis based on a generalized Anderson theorem which points to an unconventional multiband s +− -pairing state where the sign of the order parameter is different on one (or a small subset) of the smaller Fermi surface sheets but remains isotropic and overall fully gapped.

Robust superconductivity and the suppression of charge-density wave in the quasi-skutterudites Ca 3 ( Krenkel, Tanatar, Ghimire et al. 2024J. Phys.: Condens. MatterSelf Cite1000View full textAdd to dashboardCite

“…Approximately below T < 0.35T c , all curves saturate, indicating exponential attenuation and, therefore, a fully gapped state at all x. Previously, we reported exponential attenuation in pure compounds x = 0 and x = 1, indicating a fully gaped Fermi surface [26]. However, probing the robustness of the superconducting state to disorder, we found a significant reduction of the transition temperature with non-magnetic scattering and it was concluded that 3-4-13 stannides are indeed fully gapped, but their order parameter is unconventional [26].…”

“…The crystals were etched with HCl, cut with a wire saw, and polished to a typical size of (1 − 2) × 0.2 × 0.4 mm 3 . The contacts were formed by soldering 50 µm silver wires with tinsilver solder [25,26], with typical contact resistances below 100 µΩ.…”

“…The resistivity of the samples at T = 300 K ranged between 140 and 105 µΩ • cm [26]. The precision of the determination of ρ(300 K) in the alloy samples, which were typically small and irregular in shape, was not sufficient to reveal any systematic dependence on x, so we present the normalized resistivity values, which do not depend on the geometric factor.…”

“…The London penetration depth provides further insight into the magnetic properties of Ca 3 (Ir 1-x Rh x ) 4 Sn 13 Specifically, it allows examination of the genuine Meissner-London state unaffected by Abrikosov vortices and allows for conclusions regarding the superconducting gap structure. Stoichiometric compounds have previously been systematically studied and, although fully gapped, their behavior is unconventional [26,34]. A full description of the tunnel diode resonator (TDR) technique and its applications can be found elsewhere [35][36][37][38][39].…”

Development of a Geometric Descriptor for the Strategic Synthesis of Remeika Phases

“…However, the difference shown in Figure between Yb 3 Rh 4 Sn 13 and (Sn 1– x Tb x )­Tb 4 Rh 6 Sn 18 structure types resides in the prism arrangement, thus causing two distinct crystallographic sites for the A element. A detailed comparison between the Yb 3 Rh 4 Sn 13 and (Sn 1– x Tb x )­Tb 4 Rh 6 Sn 18 structure types is provided by Hodeau et al The (Sn 1– x Er x )­Er 4 Rh 6 Sn 18 structure type and its hettotype analogues have been of interest due to reports of tunability between reentrant superconductivity and magnetic ordering in (Sn 1– x Er x )­Er 4 M 6 Sn 18 (M = Rh and Os), , unconventional superconductivity in A 5 Rh 6 Sn 18 (A = Lu, Y, and Sc), − noncollinear spin structure, and disorder-enhanced nonhomogeneous superconductivity in the Y 5−δ (Rh 5.5 M 0.5 )­Sn 18 compounds …”