Topological Transition in a 3 nm Thick Al Film Grown by Molecular Beam Epitaxy

Abstract

We have performed detailed transport measurements on a 3 nm thick (as-grown) Al film on GaAs prepared by molecular beam epitaxy (MBE). Such an epitaxial film grown on a GaAs substrate shows the Berezinskii-Kosterlitz-Thouless (BKT) transition, a topological transition in two dimensions. Our experimental data shows that the MBE-grown Al nanofilm is an ideal system for probing interesting physical phenomena such as the BKT transition and superconductivity. The increased superconductor transition temperature (~2.4 K) compared to that of bulk Al (1.2 K), together with the ultrathin film quality, may be advantageous for future superconductor-based quantum devices and quantum information technology.

Doubling the superconducting transition temperature of ultraclean wafer-scale aluminum nanofilms

“…Compared to earlier studies [46] the low-temperature resistivities ρ of our Al films (including previous work done by some of the authors [34,35]) are significantly lower (for the relevant film thickness; Supplemental Material [25], Fig. S11).…”

“…Ultrathin epitaxial Al films were grown in a Varian Gen-II III-V solid-source MBE system [33][34][35]. Si, GaAs, and sapphire substrates were pretreated prior to depositing the Al films.…”