Density-of-states Fluctuation-induced Negative Out-of-plane Magnetoresistance in Overdoped Bi-2212

We analyzed the in-plane and out -of-plane m agnetoresistance (MR) f or o verdoped B i1.6Pb0.4Sr2CaCu2O8+δ (Bi-2212) s ingle crystals us ing s uperconductive f luctuation t heory, which considers the d ensity-of-states (DOS) contribution i n l ayered superconductors with the conventional s-wave pairing state. The out-of-plane results are well reproduced by the theory, implying that the large, negative out-of-plane MR as well as the sharp increase in the zero-field out-of-plane resistivityρc near the superconducting transition temperature Tc originate from the superconductive DOS fluctuation effect. On the other hand, the in-plane results are better reproduced without the D OS c ontribution (i.e., using only th e Aslamazov-Larkin (AL) contribution), which may be e xplained in terms of the d-wave superconductivity of the layered superconductors.