Superconducting Gap Structure of the Cage Compound Sc₅Rh₆Sn₁₈

Abstract

We report on the superconducting properties of the cage compound Sc 5 Rh 6 Sn 18 with T c = 5 K determined by magnetic susceptibility, electrical resistivity, and specific heat measurements. Measurements in magnetic fields indicate type-II superconductivity with the upper critical field µ 0 H c2 (0) = 7.24 T. H c2 (T ) shows a clear enhancement over the Werthamer-Helfand-Hohenberg prediction, suggesting a strong electron-phonon coupling. Specific heat data reveal that Sc 5 Rh 6 Sn 18 is indeed a strong-coupling BCS superconductor having an isotropic superconducting gap.

Anisotropic Superconductivity of the Caged Compound Y5Rh6Sn18 with Unusual Normal-State Electrical Resistivity

“…Our previous experiments have revealed unusual superconducting properties in R 5 Rh 6 Sn 18 [3,4]. A relatively strong electron-phonon coupling has been observed in Sc 5 Rh 6 Sn 18 with an isotropic superconducting gap [3].…”

“…Our previous experiments have revealed unusual superconducting properties in R 5 Rh 6 Sn 18 [3,4]. A relatively strong electron-phonon coupling has been observed in Sc 5 Rh 6 Sn 18 with an isotropic superconducting gap [3]. Whereas Lu 5 Rh 6 Sn 18 is a conventional BCS type superconductor, the gap structure of Y 5 Rh 6 Sn 18 is found to be strongly anisotropic as revealed from the specific heat (C) measurements; C(T ) exhibits a T 3 variation and C(H) indicates a √ H-like dependence [4].…”

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

“…B 12 ;B 13 ;B 23 ; 0.12(13);0.4(5);0.4(5) 0.06(12);0.5(14);-0.4(14); 0.06(14);0.6(14);-0.3(14); 0.1(2);0.3(27);0.0(25); 0.0(2);0.5(18);-0.5(17); Sc2 B 11 ;B 22 ;B 33 ; 0.33(3);0.37(3)0.56(3) 0.41(3);0.45(3);0.62(3); 0.50(4);0.55(4);0.67(4); 0.65(5);0.70(5);0.69(4); 0.64(5);0.71(5);0.83(5);; B 12 ;B 13 ;B 23 ; 0.00(3);0.02(3);0.01(3) -0.00(3);0.02(3);0.03(3); -0.02(3);0.03(3);0.02(3); -0.00(4);0.00(4);0.04(4); 0.02(4);0.03(4);0.03(4); Rh1 B 11 ;B 22 ;B 33 ; 0.28(2);0.25(2);0.51(2) 0.34(2);0.32(2);0.54(2); 0.43(2);0.41(2);0.59(2); 0.52(3);0.51(3);0.53(3); 0.49(3);0.47(3);0.68(3); B 12 ;B 13 ;B 23 ; -0.01(2);0;0 -0.02(2);0;0; -0.02(2);0;0; -0.02(2);0;0; -0.04(2);0;0; Rh2 B 11 ;B 22 ;B 33 ; 0.25(2);0.34(2);0.40(1); 0.32(1);0.41(2);0.43(1); 0.40(2);0.50(2);0.48(1); 0.49(2);0.59(2);0.45(2); 0.46(2);0.59(2);0.56(2); B 12 ;B 13 ;B 23 ;…”

Unconventional superconductivity in the cage-type compound Sc5Rh6Sn18

“…Since the normal-state heat capacity was found to be invariant under external magnetic fields, the normal-state electronic heat capacity coefficient γ and the lattice heat capacity coefficient β were deduced from the data in a field of 7.5 T where the superconductivity is completely suppressed, using a least-square fit of the C P (T )/T data to C P (T )/T = γ + βT 2 + δT 4 . The least-squares analysis of the 7.5 T data provides a Sommerfeld constant γ = 51.10 mJ/(mol-K 2 ), β = 0.13 mJ/(mol-K 4 ), δ = 0.32 mJ/(mol-K 6 ) and from this value of β we have estimated the Debye temperature Θ D = 271 K 31,32 . We have analyzed the electronic heat capacity data (below T c ) using T 3 model and the single-band α−model that was adapted from the single-band BCS theory to fit the heat capacity data that deviate from the BCS prediction 34,35 .…”

“…2(b) demonstrate a theoretical fit based upon the α− model and T 3 model. In the α− model it was assumed that the normalized gap amplitude ∆(T )/∆(0) follows the isotropic s-wave BCS result with α = ∆(0)/k B T c being an adjustable parameter 31,32 . The α-model is an excellent fit to the electronic heat capacity data of Sc 5 Rh 6 Sn 18 below T c with α = 2.65, which is significantly larger than the value for the weak-coupling BCS value of 1.76.…”