Strongly interacting Majorana modes in an array of Josephson junctions

TL;DR

This paper explores how capacitive coupling in a superconducting island array can induce interactions between Majorana modes, revealing a topological insulating phase amid competing trivial insulating states despite strong interactions.

Contribution

It introduces a model where capacitive coupling creates interactions between Majorana modes and uncovers a topological phase resulting from the competition of insulating states.

Findings

Capacitive coupling induces effective Majorana interactions.

A topological insulating phase emerges between trivial insulators.

Strong interactions do not destroy topological order.

Abstract

An array of superconducting islands with semiconducting nanowires in the right regime provides a macroscopic implementation of Kitaev's toy model for Majorana wires. We show that a capacitive coupling between adjacent islands leads to an effective interaction between the Majorana modes. We demonstrate that even though strong repulsive interaction eventually drive the system into a Mott insulating state the competition between the (trivial) band-insulator and the (trivial) Mott insulator leads to an interjacent topological insulating state for arbitrary strong interactions.