Evidence of Two-dimensional Superconducting Behavior in Atomically Thin Fe(Te_0.7Se_0.3) Flakes

We report detailed thickness-dependent transport studies on strain-free Fe(Te_0.7Se_0.3) thin flakes. Notably, we present evidence of two-dimensional superconducting behavior in flakes <10nm. For >10nm flakes we find a systematic suppression of the superconductivity and broadening of the superconducting phase transition. Due to non-uniform Te/Se spacial distribution, we find that R(T) behavior in flakes <10nm can be explained and confirmed using the BKT transition for inhomogeneity model, as well as finite state effects(FSE). This inhomogeneous model is supported by the observed thickness dependence of the superconducting transition. We propose a 2D network of superconducting paths connecting superconducting islands within Fe(Te_0.7Se_0.3) thin flakes to describe the behavior of this natural percolating system.