Unusual upper critical fields of the topological nodal-line semimetal candidate Sn$_{x}$NbSe$_{2-δ}$

Riffat Munir; K A M Hasan Siddiquee; Charuni Dissanayake; Xinzhe Hu; Yasumasa Takano; Eun Sang Choi; Yasuyuki Nakajima

doi:10.1088/1361-648X/abf386

paper

Unusual upper critical fields of the topological nodal-line semimetal candidate Sn $_{x}$ NbSe $_{2 - δ}$

arXiv:2103.08030 · doi:10.1088/1361-648X/abf386

Abstract

We report superconductivity in Sn $_{x}$ NbSe $_{2 - δ}$ , a topological nodal-line semimetal candidate with a noncentrosymmetric crystal structure. The superconducting transition temperature $T_{c}$ of this compound is extremely sensitive to Sn concentration $x$ and Se deficiency $δ$ , 5.0 K for Sn $_{0.13}$ NbSe $_{1.70}$ and 8.6 K for Sn $_{0.14}$ NbSe $_{1.71}$ and Sn $_{0.15}$ NbSe $_{1.69}$ . In all samples, the temperature dependence of the upper critical field $H_{c 2} (T)$ differs from the prediction of the Werthamer-Helfand-Hohenberg theory. While the zero-temperature value of the in-plane upper critical field of Sn $_{x}$ NbSe $_{2 - δ}$ with the higher $T_{c}$ is lower than the Pauli paramagnetic limit $H_{P}$ , that of the lower $T_{c}$ sample exceeds $H_{P}$ by a factor of $\sim$ 2. Our observations suggest that odd-parity contribution dominates the superconducting gap function of Sn $_{x}$ NbSe $_{2 - δ}$ , and it can be fine-tuned by the Sn concentration and Se deficiency.

6 pages, 6 figures

Unusual upper critical fields of the topological nodal-line semimetal candidate Snx​NbSe2−δ​

Abstract

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Unusual upper critical fields of the topological nodal-line semimetal candidate Sn $_{x}$ NbSe $_{2 - δ}$