2024/11/29 by Kumarasinghe, K., Rahman, A., Tomlinson, M. +4
#FOS: Physical sciences #Superconductivity (cond-mat.supr-con)
paper · doi:10.48550/arxiv.2411.19932
We report a systematic study of the normal-state and superconducting properties of single crystal Pb1-xSnxTaSe2 (0≤ x ≤ 0.23). Sn doping enhances the superconducting temperature Tc 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 Tc 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 PbTaSe2. Substituting Pb with more Sn lowers the specific heat jump at Tc 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 PbTaSe2 (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 Tc of Pb1-xSnxTaSe2.