paper

Observation of Two-dimensional Superconductivity in an Ultrathin Iron-Arsenic Superconductor

arXiv:2006.03338 · doi:10.1088/2053-1583/abdaba

Abstract

Two-dimensional (2D) superconductors supply important platforms for exploring new quantum physics and high- $T_{c}$ 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 KCa $_{2}$ Fe $_{4}$ As $_{4}$ F $_{2}$ . For the sample with the thickness of 2.6 $\sim$ 5 nm (1 $\sim$ 2 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 $T_{c}$ , 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 KCa $_{2}$ Fe $_{4}$ As $_{4}$ F $_{2}$ .

5 pages, 4 figures