Enhancement of the superconducting transition temperature due to multiband effect in the topological nodal-line semimetal Pb$_{1-x}$Sn$_{x}$TaSe$_{2}$

K. Kumarasinghe; A. Rahman; M. Tomlinson; D. Le; F. Joshua; L. Zhai; Y. Nakajima

doi:10.1103/hsdq-2tp9

paper

Enhancement of the superconducting transition temperature due to multiband effect in the topological nodal-line semimetal Pb $_{1 - x}$ Sn $_{x}$ TaSe $_{2}$

arXiv:2411.19932 · doi:10.1103/hsdq-2tp9

Abstract

We report a systematic study of the normal-state and superconducting properties of single crystal Pb $_{1 - x}$ Sn $_{x}$ TaSe $_{2}$ $(0 \leq x \leq 0.23)$ . Sn doping enhances the superconducting temperature $T_{c}$ up to 5.1 K while also significantly increasing impurity scattering in the crystals. For $x = 0$ and 0.018, the specific heat jump at $T_{c}$ exceeds the Bardeen-Cooper-Schrieffer (BCS) weak-coupling value of 1.43, indicating the realization of strong-coupling superconductivity in undoped and slightly Sn-doped PbTaSe $_{2}$ . Substituting Pb with more Sn lowers the specific heat jump at $T_{c}$ below the BCS value of 1.43, which cannot be explained by a single-gap model. Rather, the observed specific heat data of moderately Sn-doped PbTaSe $_{2}$ ( $x = 0.08$ and 0.15) are reproduced by a two-gap model. Our density functional theory calculations suggest that three-dimensional Fermi pockets appear due to a reduction of the spin-orbit gap with Sn doping, and the multiband effect arising from these emergent Fermi pockets enhances the effective electron-phonon coupling strength, leading to the increase in $T_{c}$ of Pb $_{1 - x}$ Sn $_{x}$ TaSe $_{2}$ .

7 pages, 4 figures

Enhancement of the superconducting transition temperature due to multiband effect in the topological nodal-line semimetal Pb1−x​Snx​TaSe2​

Abstract

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Enhancement of the superconducting transition temperature due to multiband effect in the topological nodal-line semimetal Pb $_{1 - x}$ Sn $_{x}$ TaSe $_{2}$