Nanofabrication of Sn-based superconductor / topological Dirac semimetal heterostructures

The superconductor/topological-material heterostructures attract attention as a platform of unconventional superconductivity. Among various topological material candidates, α-Sn is attractive because it can exhibit a wide range of topological phases from topological Dirac semimetal to topological insulator. Moreover, upon heating α-Sn undergoes a phase transition to β-Sn, which becomes superconducting at low temperature (< 4 K). In this study, we utilize this rich phase diagram of Sn to fabricate superconducting β-Sn/topological Dirac semimetal α-Sn planar junctions. Epitaxial α-Sn thin films are partially transformed to β-Sn under Ga ion-beam irradiation, which exhibits superconductivity at 3.8 K. By focusing the ion beam, we successfully fabricate β-Sn nanowire structures with less than 200 nm in width. In the presentation, we will discuss the structure and superconducting properties of the nanostructure in detail.