Superconductivity in the Surface State of Noble Metal Gold and its Fermi Level Tuning by EuS Dielectric

Abstract

The induced superconductivity (SC) in a robust and scalable quantum material with strong Rashba spin-orbit coupling is particularly attractive for generating topological superconductivity and Majorana bound states (MBS). Gold (111) thin film has been proposed as a promising candidate because of the large Rashba energy, the predicted topological nature, and the possibility for large-scale MBS device fabrications. We experimentally demonstrate two important steps towards achieving such a goal. We successfully show induced SC in the Shockley surface state (SS) of ultrathin Au(111) layers grown over epitaxial vanadium films, which is easily achievable on a wafer scale. The emergence of SC in the SS, which is physically separated from a bulk superconductor, is attained by indirect quasiparticle scattering processes instead of by conventional interfacial Andreev reflections. We further show the ability to tune the SS Fermi level (EF) by interfacing SS with a high-κ dielectric ferromagnetic insulator EuS. The shift of EF from ∼550 to ∼34 mV in superconducting SS is an important step towards realizing MBS in this robust system.

Source-reported materials — not catalogue approval

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