Unusual superconductivity in the topological nodal-line semimetal candidate SnxNbSe2-δ

• Main Authors: Riffat Munir, K A M Hasan Siddiquee, Dissanayake, Charuni, Kapila Kumarasinghe, Hu, Xinzhe, Takano, Yasumasa, Choi, Eun Sang, Nakajima, Yasuyuki
• Format: Conference Proceeding
• Language: English
• Subjects: Critical field (superconductivity); Crystal structure; Physics; Superconductivity; Temperature dependence; Topological superconductors; Transition temperature
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/2164/1/012008

We report the superconductivity of the topological nodal-line semimetal candidate SnxNbSe2-δ with a noncentrosymmetric crystal structure. The superconducting transition temperature Tc of SnxNbSe2-δ drastically varies with the Sn concentration x and the Se deficiency δ, and reaches 12 K, relatively higher than those of known topological superconductors. The upper critical field of this compound shows unusual temperature dependence, inconsistent with the WHH theory for conventional type-II superconductors. In a low-Tc sample, the zero-temperature limit of the upper critical field parallel to the ab plane exceeds the Pauli paramagnetic limit estimated from the simple BCS weak coupling model by a factor of ∼ 2, suggestive of unusual superconductivity stabilized in SnxNbSe2-δ. Together with the robust superconductivity against disorder, these observations indicate that SnxNbSe2-δ is a promising candidate to explore topological superconductivity.