Proximity induced superconductivity in epitaxial Nb/Au(111) bilayers

Majorana zero modes (MZM) are novel quasi-particle excitations that are most accessible to experiments through hybrid systems combining spin-orbit coupling, superconductivity, and magnetism. Recent work demonstrates that a pair of MZMs can emerge in a heterostructure of epitaxial Au(111) sandwiched between superconducting vanadium and the magnetic insulator EuS [1,2]. The induced superconducting gap in the Au (111) layer topologically protects the MZMs. In this talk, we present our work in swapping the vanadium layer with niobium (Nb) in order to increase the size of the induced gap. We use molecular beam epitaxy to grow epitaxial Au (111) of various thicknesses on 8nm of epitaxial Nb (110). The sample quality is confirmed by x-ray diffraction and in-situ reflection high energy electron diffraction. In addition, evolution of the induced gap as a function of the film thickness is examined by point contact Andreev reflection (PCAR). Magnetic field dependent PCAR measurements are also discussed.

[1] S. Manna, P. Wei, Y. Xie, K. T. Law, P. A. Lee & J. S. Moodera, PNAS 117 (16) 8775-8782 (2020)
[2] P. Wei, S. Manna, M. Eich, P. A. Lee & J. S. Moodera, Phys. Rev. Lett. 122, 247002 (2019).