Superconducting proximity effect in YB₆/SmB₆ bilayer thin films

Topological superconductivity has been predicted to arise in a topological insulator (TI) in contact with a trivial superconductor by virtue of proximity effect, harboring Majorana excitations [1]. The topological Kondo insulator SmB₆ is an ideal candidate to explore such TI-based quantum phenomena due to its robust insulating bulk properties as well as the conducting surface states [2]. In this work, we study the superconducting proximity effect using bilayer thin films consisting of SmB₆ and superconducting YB₆ due to their excellent lattice match. The superconducting properties of YB₆ have been reported to be strongly dependent on the stoichiometry [3] with the maximum T_c observed in boron deficient samples. We have grown high quality thin films of SmB₆ and YB₆ by cosputtering method in an ultrahigh-vacuum-compatible chamber. The growth parameters have been optimized through microstructural characterizations and magneto-transport measurements. The induced superconductivity in the SmB₆ thin films has been studied via proximity electron tunneling spectroscopy.

[1] L. Fu & C. L. Kane, Phys. Rev. Lett. 100, 096407 (2008).

[2] M. Dzero et al., Annu. Rev. Condens. Matter Phys. 7, 249 (2016); W. K. Park et al., Proc. Natl. Acad. Sci. U.S.A. 113, 6599 (2016).

[3] N. Sluchanko et al., Phys. Rev. B. 96, 144501 (2017); S. Lee et al., Nature 570, 344–348 (2019).