Evidence fors-wave superconductivity in noncentrosymmetric Re24Nb5from

Chin‐Shan Lue

¹

,

T. H. Su

²

,

H. F. Liu

³

et al.

Abstract

We report a 93 Nb nuclear magnetic resonance (NMR) study on the noncentrosymmetric superconductor Re 24 Nb 5. Below the superconducting temperature T c (H), the spin susceptibility probed by the 93 Nb NMR Knight shift gradually decreases with lowering temperature, accompanied by the broadening of the resonance spectrum. Such behavior is commonly observed in the BCS-type superconductors. The 93 Nb NMR spin-lattice relaxation rate (1/T 1) shows a well-defined coherence peak just below T c (H), followed by a marked decrease with further decreasing temperature. Moreover, the 1/T 1 data in the superconducting state were found to obey a single exponential expression, yielding a nodeless gap /k B = 10.3 K. This value gives the ratio of 2 /k B T c (H) = 3.55, that is almost identical with the value of 3.5 predicted from BCS theory. On these bases, we conclude that the noncentrosymmetric Re 24 Nb 5 compound can be characterized as a weakly coupled BCS-type superconductor.

Electronic structure of non-centrosymmetric superconductors Re24(Nb;Ti)5 by ab initio calculations

“…217) unit cell (u.c. ), a = 0.96076 nm [5] and 0.9581 nm [7] were used for Re 24 Nb 5 and Re 24 Ti 5 , respectively. The atomic positions were fully optimised.…”

“…The recent renewal of an interest in this family of compounds [5,6,7] is connected with a search of unusual properties of a superconducting state in non-centrosymmetric systems. The lack of spatial inversion symmetry leads to the antisymmetric spin-orbit coupling (ASOC) that lifts the Krammers degeneracy and may induce a mixture of spin singlet and triplet states in the superconducting phase [8,9,10,11].…”

“…Despite the fact that in Re-based compounds the strength of ASOC is expected to be relatively strong, the superconducting state in Re 24 Nb 5 (T SC = 8.7 K [5]), Re 23. 8 Nb 5.2 (T SC = 8.8 K [6]), and Re 24 Ti 5 (T SC = 5.8 K [7]) exhibits rather a BCS-like behaviour.…”

“…The superconducting properties in Re 24 (Nb;Ti) 5 intermetallics, adopting the α-Mn type structure [1], have been studied since 1960s [2,3,4]. The recent renewal of an interest in this family of compounds [5,6,7] is connected with a search of unusual properties of a superconducting state in non-centrosymmetric systems.…”

Weak ferromagnetism in a noncentrosymmetric BiPd 4 K superconductor

“…CePt 3 Si [1] has attracted great attention of condensed matter physics community. Similarly, some other noncentrosymmetric superconductors have been studied in recent past with conventional superconducting behavior such as Ru 7 B 3 , Mg 10 Ir 19 B 16 , α-BiPd, and the cubic phases of Re 3 W, and Re 24 Nb 5 [2][3][4][5][6][7]. Further, superconductivity has been reported in ntype metallic interface being formed between the LaAlO 3 and SrTiO 3 interface, which is naturally an inversion symmetry system without up-down reflection [8].…”