Electrically controlled crossover between $2\pi$- and $4\pi$-Josephson effects through topologically-confined channels in silicene

TL;DR

This paper introduces a tunable topological Josephson junction in silicene that can switch between trivial and topological states via electrostatic gating, enabling control over $2 extpi$- and $4 extpi$-Josephson effects.

Contribution

It demonstrates an electrically tunable topological phase transition in silicene junctions, controlling valley-chiral states and intervalley scattering for advanced quantum device applications.

Findings

Analytical and numerical calculations of Andreev bound states.

Electrical switching of intervalley scattering in the junction.

Realization of a topological Josephson junction with tunable quasiparticle poisoning.

Abstract

We propose a tunable topological Josephson junction in silicene where electrostatic gates could switch between a trivial and a topological junction. These aspects are a consequence of a tunable phase transition of the topologically confined valley-chiral states from a spin-degenerate to a spin-helical regime. We calculate the Andreev bound states in such a junction analytically using a low-energy approximation to the tight-binding model of silicene in proximity to s-wave superconductors as well as numerically in the short- and long-junction regime and in the presence of intervalley scattering. Combining topologically trivial and non-trivial regions, we show how intervalley scattering can be effectively switched on and off within the Josephson junction. This constitutes a topological Josephson junction with an electrically tunable quasiparticle poisoning source.