Logical Majorana zero modes in a nanowire network

Abstract

We present a scheme to use physical Majorana quasi-zero modes at each junction of a two-dimensional nanowire network to build a logical Majorana zero mode, the location of which is controllable through gate voltages. The wire-network is a way to realize a proposal by Yang et al. arXiv:1808.04825 to imprint a Kekul\'e vortex pattern on a honeycomb lattice via gate voltages. We show that a specific type of junction -- other than a naive Y- or T-junction -- is needed to realize, without breaking time-reversal symmetry, an artificial ``graphene'' system with Majorana fermions instead of complex ones at each site. The junction we propose (i) traps exactly one physical Majorana (quasi-)zero mode at each site of either a brick wall or honeycomb lattice and (ii) allows this mode to hybridize with all three neighboring sites. Using a lattice of these junctions and starting from an electronic, tight-binding model for the wires, we imprint the voltage patterns corresponding to the Kekul\'e vortex and observe the emergence of the logical Majorana zero mode at the vortex core. We also provide the range of parameters where this excitation could be realized experimentally.