Time-Reversal Invariant Topological Superconductivity in Planar Josephson Bijunction

TL;DR

This paper demonstrates that a planar Josephson bijunction with strong Rashba spin-orbit interaction can be tuned into a time-reversal invariant topological superconducting phase hosting Majorana bound states, using external gates.

Contribution

It introduces a controllable method to realize time-reversal invariant topological superconductivity in a planar Josephson bijunction with Rashba layers.

Findings

Topological phase can be achieved with small tunneling amplitudes.

Majorana bound states are localized at the ends of the normal region.

External gates enable tuning into the topological phase.

Abstract

We consider a Josephson bijunction consisting of a thin $SIS$ $\pi$-Josephson junction sandwiched between two-dimensional semiconducting layers with strong Rashba spin-orbit interaction. Each of these layers forms an $SNS$ junction due to proximity-induced superconductivity. The $SIS$ junction is assumed to be thin enough such that the two Rashba layers are tunnel-coupled. We show that, by tuning external gates, this system can be controllably brought into a time-reversal invariant topological superconducting phase with a Kramers pair of Majorana bound states being localized at the end of the normal region for a large parameter phase space. In particular, in the strong spin-orbit interaction limit, the topological phase can be accessed already in the regime of small tunneling amplitudes.