Multi-band Superconductivity in a misfit layered compound (SnSe)1.16(NbSe2)2

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 c 2 ab (0) is 1.74 times the value of Pauli paramagnetic limit. Moreover, there is a positive curvature in the H c 2 ( T ) 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 ).