Topological YB₆/SmB₆/YB₆ trilayer Josephson junctions

Samarium hexaboride (SmB₆) is a topological Kondo insulator (TKI) characterized by robust topological surface states and true bulk insulation. Previously, we demonstrated perfect Andreev reflection in epitaxial heterostructures consisting of s-wave superconductor YB₆ and TKI SmB₆ as a signature of topologically protected superconducting Klein tunneling [1]. Here, we report fabrication of topological Josephson junctions based on YB₆/SmB₆/YB₆ trilayers for pursuing a reliable and scalable topological qubit architecture. Epitaxial YB₆/SmB₆/YB₆ films were grown on 3” Si wafers by in-situ co-sputtering to secure uniform and pristine junction interfaces, and vertical Josephson junction arrays were made using microfabrication based on standard photolithography. The junctions display the resistively-shunted junction characteristics in I–V curves and well-behaved Fraunhofer diffraction patterns. Robust cell-to-cell and chip-to-chip uniformity was observed in R_NA across multiple junctions suggestive of topologically protected device performance. The dependence of junction properties on the SmB₆ barrier thickness will be discussed.

[1] S. Lee et al. Nature 570, 344–348 (2019).