Observation of Two-dimensional Superconductivity in an Ultrathin Iron-Arsenic Superconductor
Abstract
Two-dimensional (2D) superconductors supply important platforms for exploring new quantum physics and high-Tc superconductivity. The intrinsic superconducting properties in the 2D iron-arsenic superconductors are still unknown owing to the difficulties in the preparation of ultrathin samples. Here we report the fabrication and physical investigations of the high quality single-crystalline ultrathin films of the iron-arsenic superconductor KCa2Fe4As4F2. For the sample with the thickness of 2.65 nm (12 unit cells), a sharp superconducting transition at around 30 K (onset point) is observed. Compare with the bulk material, the ultrathin sample reveals a relatively lower Tc, wider transition width, and broader flux liquid region under the in-plane field. Moreover, the angle dependent upper critical field follows the Tinkham model, demonstrating the two-dimensional superconductivity in ultrathin KCa2Fe4As4F2.