Abstract
We report the successful growth of high-quality single crystals of LiFeAs with lateral sizes up to 5×5 mm2 by the Sn-flux method. Electrical resistivity studies reveal that the superconducting onset temperature is 18.2 K with a transition width less than 1.1 K and the ratio of room temperature to residual resistivity is about 24. Bulk superconductivity is supported by perfect shielding in the magnetic susceptibility and a clear jump in the specific heat Cp, resulting in ΔCp/T ≈ 20.0 mJ/mol K2. Upper-critical-field slopes of dHc2c/dT ≈−1.39 and dHc2ab/dT ≈−2.99 T/K near Tc predict zero-temperature upper critical fields of Hc2c(0) ≈ 17.2 and Hc2ab(0) ≈ 36.9 T and coherence lengths of ξab=4.4 and ξc=2.0 nm in a single-band model. This result points to a modest superconducting anisotropy about 2.3 in LiFeAs.
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Accepted by G. A. Sawatzky