Josephson Junction

 Topological superconductors have a Majorana bound state (MBS) at their boundaries or vortices on the surface [1]. Such MBS follow non-Abelian exchange statistics, so they can be used as a fault-tolerant topological quantum computer [2], FeTe_0.55Se_0.45 (FTS), an iron-based superconductor, is one of the candidates for topological superconductors [3]. FTS is expected to have a topological surface state and zero-energy vortex bound state (ZVBS) under the external magnetic field [4]. To prove the topological superconductivity of FTS, we fabricated full-van der Waals vertical Josephson junction through low-temperature micro-cleaving technique. We will discuss our investigation about the Shapiro steps upon irradiating microwave as a function of the strength of the external magnetic field.

[1] Rev. Mod. Phys.. 82, 4. (2010)

[2] Phys. –Usp. 44, 131 (2001)

[3] PRL. 117, 047001 (2016)

[4] Nature Materials. 18, 811-815 (2019)