Superconducting single-atomic-layer Tl-Pb compounds on Ge(111) and Si(111) surfaces.

Abstract The set of known single-atomic-layer (SAL) superconductors has been limited so far by a few examples, including Si(111)-hex- 7 × 3 -In reconstruction, Si(111)-SIC-Pb and -HIC-Pb phases, and Si(111) 3 × 3 -(Tl, Pb) compound phase. In the present study where transport properties of SAL compounds of Tl-Pb with different composition ratios on Ge(111) and Si(111) substrates have been studied in situ in ultrahigh vacuum, the list of SAL superconductors has been enlarged by three new members, Ge(111) 3 × 3 (Tl, Pb), Ge(111)3×3-(Tl, Pb), and Si(111)4×4-(Tl, Pb) systems which show superconducting transition at the critical temperatures of 2.03 K, 0.83 K and 0.79 K, respectively. Bearing in mind that the atomic arrangements and electronic band structures of these SAL compounds of Tl-Pb have already been established, the obtained data set is believed to constitute a solid basis for the prospective theoretical investigations on the nature of SAL superconductivity. In addition, all the new systems demonstrate a noticeable Rashba-type spin splitting in the metallic surface-state bands and, therefore, they might be promising materials for future superconducting spintronics as well as for basics research of exotic superconductivity. Graphical Abstract Unlabelled Image Highlights • Three new single-atomic-layer superconductors have been found. • These are Ge(111) 3 × 3 − (Tl, Pb), Ge(111)3 × 3 −(Tl, Pb) and Si(111)4 × 4 −(Tl, Pb) 2D compounds. • They show superconducting transitions at T c of 2.03 K, 0.83 K and 0.79 K, respectively. • The role of a substrate and a layer composition on their superconducting properties is discussed. [ABSTRACT FROM AUTHOR]