Upper critical fields and superconducting anisotropy of K +_(0.70)Fe_(1.55)Se_(1.01)S_(0.99) and K _(0.76)Fe~(1.61)Se_(0.96)S_(1.04) single crystals

摘要

We have investigated temperature and angular dependence of resistivity of K_(0.70(7))Fe_(1.55(7))Se_(1.01(2))S_(0.99(2)) and K_(0.76(5))Fe_(1.61(5))Se_(0.96(4))S _(1.04(5)) single crystals. The upper critical fields μ_0H_(c2)(T) for both field directions decrease with the increase in S content. On the other hand, the angle-dependent magnetoresistivity for both compounds can be scaled onto one curve using the anisotropic Ginzburg-Landau theory. The obtained anisotropy of μ_0H _(c2)(T) increases with S content, implying that S doping might decrease the dimensionality of certain Fermi surface parts, leading to stronger two-dimensional character.