Superconductivity in a misfit compound (PbSe)1.12(TaSe2)

We report the discovery of superconductivity with a maximum {\em T}$_c \approx$ 1.28 K in Br-doped (PbSe)$_{1.12}$(TaSe$_2$), which is a new misfit compound consisting of alternating layers of distorted rocksalt PbSe and dichalcogenide TaSe$_2$. It is found that the Br-doping is required for the formation of this misfit compound and superconductivity can be tuned by Br content. The large anisotropic parameter of resistivity ${\gamma}_\rho$ = ${\rho_c}$/${\rho_{ab}}$ $\approx$ 100 and that of upper critical field $\gamma_{H_{c2}}$ = $H_{c2}^{ab} /H_{c2}^{c}$ $\approx$ 10 are obtained. The estimated $c$-axis coherence length ${\xi}$$_c$ $\approx$ 6.3 nm, larger than the $c$-axis lattice constant, which implies that this compound is an anisotropic three-dimensional superconductor. The Hall coefficient measurements suggest that the charge transport is dominated by the hole-type charge carrier and there is a charge transfer from the PbSe layer to the conducting TaSe$_2$ layer. The small normalized specific heat jump $\Delta C/\gamma T_c$ = 1.16 and electron-phonon coupling constant $\lambda_{ep}$ $\approx$ 0.61 indicate that Br-doped (PbSe)$_{1.12}$(TaSe$_2$) is a weak-coupling BCS superconductor.