Superconductivity in a misfit layered compound (SnSe)${}_{1.16}$(NbSe${}_2$)

Abstract

The large size single crystals of (SnSe)${}_{1.16}$(NbSe${}_2$) misfit layered compound were grown and superconductivity with $T_c$ of 3.4 K was first discovered in this system. Powder X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) clearly display the misfit feature between SnSe and NbSe${}_2$ subsystems. The Sommerfeld coefficient ${\hat{I}}^3$ inferred from specific-heat measurements is 16.73 mJ mol${}^{-1}$ K${}^{-2}$, slightly larger than the usual misfit compounds. The normalized specific heat jump $\hat{I}”$$C_e$/${\hat{I}}^3$$T_{\mathrm{c}}$ is about 0.98, and the electron-phonon coupling constant $\hat{I}»$${}_{e-ph}$ is estimated to be 0.80. The estimated value of the in-plane upper critical magnetic field, $H_{c2}^{ab}$(0), is about 7.82 T, exceeding the Pauli paramagnetic limit slightly. Both the specific-heat and $H_{c2}$ data suggest that (SnSe)${}_{1.16}$(NbSe${}_2$) is a multi-band superconductor.

7 pages,5 figures, to be published in JPCM