Multi-band Superconductivity in a misfit layered compound (SnSe)_1.16(NbSe₂)₂

Abstract

We report the discovery of superconductivity with T c of about 5.3 K in a new misfit layered compound (SnSe) 1.16 (NbSe 2 ) 2 . High resolution transmission electron microscopy and selected area electron diffraction of the single-crystalline samples clearly reveal the misfit layered structure. Based on the McMillan equation, the electron-phonon coupling constant λ e-ph is estimated to be about 0.96, which is close to strong coupling range. The estimated out-of-plane and in-plane upper critical magnetic fields are 8.9 T and 15.5 T respectively. H ab c2 (0) is 1.74 times the value of Pauli paramagnetic limit. Moreover, there is a positive curvature in the ( ) H T c2 curves near T c , indicating a feature of multi-band superconductivity. The temperature dependence of specific-heat in superconducting state can be fit by a two-band BCS model, which confirms further the multi-band superconductivity. The reduced charge transfer between the two subsystems may account for the enhanced T c comparing with (SnSe) 1.16 (NbSe 2 ).

Enhanced anisotropic superconductivity in the topological nodal-line semimetal InxTaS2

“…Unfortunately, the guided relation between T c and layer distance d or Γ in these TMDs-related compounds seem not to be widely concluded. However, intercalated layered compounds seems a good method to possess highly anisotropic superconductivity and large H ||ab c2 in bulk state, even exceeding the Pauli limit H p 31,[42][43][44] . According to the anisotropic Ginzburg-Landau formulas, and ξ c at zero temperature are calculated for four samples.…”

Protection of Ising spin-orbit coupling in bulk misfit superconductors

“…It is plausible that these insights can be extended to other misfit compounds and bulk structures comprising transition-metal dichalcogenide layers, where large in-plane critical magnetic fields that exceed the Pauli limit have been reported but not identified as evidence of Ising superconductivity. This includes works on (SnSe) 1.16 (NbSe 2 ) 2 [33], Ba 6 Nb 11 S 28 [34], cation-intercalated NbSe 2 [35], and organometallic intercalated compounds of 2H-TaS 2 [36,37]. Future experiments and theory work to determine the electronic and structural properties for this broad range of potential bulk Ising superconductors will be of great interest.…”