Surface superconductivity in gold – a material platform for Majorana bound states*

Proximity effect in multilayer heterostructures allows the creation of new quasiparticles with mixed physical characters. In particular, it may lead to the emergence of Majorana bound states (MBS) by mixing superconductivity, ferromagnetism, and spin-orbit coupling at material interfaces. Inducing superconductivity and magnetic exchange interactions in well-defined Shockley surface states (SS) of high quality ultrathin Au(111) layers has been predicted as an excellent platform for MBS [1]. In this talk, I will first present our device based heterostructure platform for creating and investigating such hybrid superconducting states in Au(111) [2]. By means of electron tunneling spectroscopy, I will demonstrate signatures of superconductivity induced in the two-dimensional SS of Au(111) thin film, as well as the behavior of such superconducting state under a planar Zeeman field. Unlike conventional proximity effects, the induced superconductivity in SS that are physically separated from a bulk superconductor may be governed by indirect quasiparticle scattering processes, which would further allow the manipulations of SS for MBS. Our results on planar tunneling devices made of scalable nanowires fabricated from such Au(111) heterostructures will be discussed.
[1.] Potter, A. C. and Lee, P. A., Phys. Rev. Lett. 105, 227003 (2010), Phys. Rev. B 85, 094516 (2012)
[2.] Wei, P., et. al., Nano Lett. 16 (4), 2714–2719 (2016)