Single crystal growth and superconducting properties of LiFeAs

LiFeAs, a representative compound for `111' system of Fe-based superconductors, has a tetragonal Cu$_{2}$Sb-type structure and possesses a single Fe-As tetrahedral layer sandwiched by the double Li layers. This structural characteristic provides a unique opportunity to realize homogeneous Li terminating surface upon cleaving, and this possibility makes LiFeAs attractive for investigating the intrinsic properties of Fe-based superconductors with various spectroscopic tools. In this sense, growing a large LiFeAs single crystal is a necessary step for studying intrinsic properties of the Fe-based superconductors. We report the successful growth of high quality LiFeAs single crystal by Sn-flux. Electrical resistivity studies reveal the superconducting onset temperature is 18.2 K with a transition width less than 1.1 K and RRR is about 24. Bulk superconductivity is supported by perfect shielding in the magnetic susceptibility and a clear jump in the specific heat. Upper critical field slopes of d$H_{c2}^{c}$/d$T\approx $-1.39 and d$H_{c2}^{ab}$/d$T\approx $-2.99 T/K near $T_{c}$ predict $H_{c2}^{c}$(0)$\approx $17.2 and $H_{c2}^{ab}$(0)$\approx $36.9 T, and it points to a modest superconducting anisotropy about 2.3 near $T_{c}$. This observed modest anisotropy is a bit smaller than the band calculation results based on the GGA approximation but larger than the prediction considered effects of electron correlation through the dynamic mean field theory.