Observation of Superconductivity by Sr Intercalation in Topological Insulator Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$

Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$ is a well-known 3D topological insulator. Here we show that Sr intercalation into the van der Waal gaps of Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$ induces superconductivity with a maximum T$_{\mathrm{c}}$ of 2.9 K. The single crystals of Sr$_{\mathrm{x}}$Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$ for x$=$ 0 to 0.2 were prepared by self-flux method. The optimally doped sample Sr$_{\mathrm{0.1}}$Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$ shows a large superconducting shielding fraction of 93{\%} with T$_{c-onset}$ of 2.94 K. Using transport measurement, the anisotropy in Sr$_{\mathrm{0.1}}$Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$ is found to be $\Gamma \quad =$ 1.5 with an upper critical field H$_{c2}$(0) equal to 2.1 T for magnetic field applied along the \textit{ab} plane of the sample. Along \textit{ab} plane of the sample, the lower critical field H$_{c1,ab}$(0) is estimated to be 0$.$39 \textpm 0$.$02 mT. Hall and Seebeck measurements shows electroninc carrier concentration of $n =$ 1$.$85 \texttimes 10$^{\mathrm{19}}$ cm$^{\mathrm{-3}}$ at 10 K. Such low carrier concentration indicates the possibility of unconventional pairing state.