Gap reopening as signature of coupling between Majorana zero modes in Sn-(Bi,Sb)2(Te,S)3-based Josephson trijunctions

TL;DR

This paper reports the experimental observation of gap reopening in coupled Majorana zero modes within Josephson trijunctions on topological insulators, supporting the Fu-Kane topological quantum computation scheme.

Contribution

First experimental demonstration of coupling effects between Majorana zero modes in adjacent Josephson trijunctions on topological insulators.

Findings

Gap reopens in phase space where closure was expected in independent junctions

Supports the Fu-Kane theory of Majorana modes in topological insulators

Enhances confidence in topological quantum computation schemes

Abstract

In the past two decades, enormous efforts have been made to search for possible platforms and schemes to implement topological quantum computation (TQC). In exploring the Fu-Kane scheme of TQC based on Josephson trijunctions constructed on topological insulators, the expected Majorana phase diagram of a single trijunction has been experimentally verified. If Majorana zero modes indeed exist in this kind of trijunctions, coupling between them in multiple trijunction devices would be further expected. In this study, we fabricated Josephson devices containing two adjacent Josephson trijunctions on the surface of Sn-(Bi,Sb)2(Te,S)3, and observed that the minigap reopens for both trijunctions in their phase spaces where a closure would otherwise be expected if the trijunctions existed independently. Our findings would provide new experimental support for the validity of the Fu-Kane theory and instill further confidence in advancing along the TQC scheme proposed by Fu and Kane.