Two-dimensional Superconductivity in Misfit Layered Compound (BiSe)_1.10NbSe₂

Novel two-dimensional superconductivity in a misfit layered compound (BiSe) 1.10 NbSe 2 with a critical temperature T c of 2.7 K is reported. The temperature dependence of H c2 is linear close to T c for both H ∥ c -axis and H ∥ ab -plane, suggesting that the superconductivity is three-dimensional with some anisotropy. However, the angular dependence of H c2 clearly reveals a cusp-like behavior, which can be explained by Tinkham model, indicating that the system is two-dimensional. In order to clarify the relationship between stripe structures on the surface and the two-dimensional superconductivity, we also performed the same measurement on a uniform microbridge sample. We found similar two-dimensional behavior even in a microbridge without linear defects, indicating that the origin of two-dimensional superconductivity in (BiSe) 1.10 NbSe 2 is not related to the stripe structure.