Transport properties and anisotropy of Rb1-xFe2-ySe2 single crystals

Single crystals of Rb1-xFe2-ySe2 are successfully synthesized with superconducting transition temperatures T-c approximate to 31 - 32.5 K. A clear humplike anomaly of resistivity was observed in the normal state in the temperature region T-an of 150 K-186 K, as found in a similar system, KxFe2-ySe2. It is found that the Meissner screening volume and the superconducting transition temperatures are higher for the sample with higher T-an, indicating that the hump of resistivity is strongly related to the superconductivity. The upper critical field has been determined with the magnetic field along the ab plane and c axis for two typical samples with different T-an, yielding an anisotropy of Gamma approximate to 3.5 when T-an = 150 K, while Gamma approximate to 4.8 when T-an = 186 K. The angle-dependent resistivity measured below T-c allow a perfect scaling feature based on the anisotropic Ginzburg-Landau theory, leading to consistent values of the anisotropy. Comparing with the anisotropy determined for Ba0.6K0.4Fe2As2 and Ba(Fe0.92Co0.08)(2)As-2 using the same method, we find that the present sample is more anisotropic and the Fermi surfaces with stronger two-dimensional characters are expected.