Fully gapped superconductivity and topological aspects of the noncentrosymmetric superconductor TaReSi

Abstract

We report a study of the noncentrosymmetric TaReSi superconductor by means of the muon-spin rotation and relaxation (μSR) technique, complemented by electronic band-structure calculations. Its superconductivity, with T c = 5.5 K and upper critical field μ 0 H c2 (0) ∼ 3.4 T, was characterized via electrical-resistivity and magneticsusceptibility measurements. The temperature-dependent superfluid density, obtained from transverse-field μSR, suggests a fully gapped superconducting state in TaReSi, with an energy gap 0 = 0.79 meV and a magnetic penetration depth λ 0 = 562 nm. The absence of a spontaneous magnetization below T c , as confirmed by zerofield μSR, indicates a preserved time-reversal symmetry in the superconducting state. The density of states near the Fermi level is dominated by the Ta-and Re-5d orbitals, which account for the relatively large band splitting due to the antisymmetric spin-orbit coupling. In its normal state, TaReSi behaves as a three-dimensional Kramers nodal-line semimetal, characterized by an hourglass-shaped dispersion protected by glide reflection. By combining nontrivial electronic bands with intrinsic superconductivity, TaReSi is a promising material for investigating the topological aspects of noncentrosymmetric superconductors.

Probing the superconducting pairing of the La4Be33Pt16 alloy via muon-spin spectroscopy

“…Considering that all these materials share similar electronic band structures with La 4 Be 33 Pt 16 , they too are expected to be conventional superconductors. At the same time, there are also many NCSCs which, despite a significant E SOC , exhibit conventional superconducting properties, characterized by a fully-gapped SC with a preserved TRS [45][46][47][48][49]. Clearly, in NCSCs, the relationship between the unconventional SC and ASOC is not yet fully understood, and further efforts, including the search for new NCSCs, are highly desirable.…”

“…Below T c , it exhibits the breaking of TRS, as well as nodes in the superconducting gap [16,44]. Although many NCSCs show a relatively large ASOC, they still behave as conventional superconductors, characterized by a nodeless SC with preserved TRS, both typical features of spin-singlet pairing [45][46][47][48][49]. Clearly, it is of great interest to search for other NCSCs which exhibit triplet pairing or breaking of the TRS and, thus, behave as unconventional-or topological superconductors.…”

Intrinsic Coherence Length Anisotropy in Nickelates and Some Iron-Based Superconductors

“…Outstanding differences between absolute values defined by different criteria were recently demonstrated in isotropic superconductor TaReSi by Shang et al [ 96 ], and for anisotropic superconductor LaFeAsO by Zhigadlo et al [ 97 ], while the vanishing of the diamagnetic response [ 96 , 97 , 98 , 99 ] remains the most accurate criterion to determine the upper critical field. In regard to the anisotropy, which is the topic of the study, different criteria of the definition lead to not only different values, but also to the change in the function trend, i.e., decrease/increase type [ 97 ].…”

Intrinsic Coherence Length Anisotropy in Nickelates, and Some Pnictides and Chalcogenides Superconductors

“…Outstanding differences between absolute B c2 (T) values defined by different criteria were recently demonstrated in isotropic superconductor TaReSi by Shang et al [96], and for anisotropic superconductor LaFeAsO by Zhigadlo et al [97], while the vanishing of the diamagnetic response [96][97][98][99] remains the most accurate criterion to determine the upper critical field. In regard to the B c2 (T) anisotropy, which is the topic of the study, different criteria of the B c2 (T) definition lead to not only different γ ξ (T) values, but also to the change in the function trend, i.e., decrease/increase type [97].…”