# Flux-Stabilized Majorana Zero Modes in Coupled One-Dimensional Fermi Wires

## TL;DR

This paper demonstrates a new method to stabilize Majorana zero modes in coupled 1D fermionic wires by applying a synthetic magnetic flux, overcoming the destructive effects of interchain tunneling.

## Contribution

It introduces a flux-based mechanism that preserves Majorana modes in 1D fermionic ladders despite significant interchain tunneling.

## Key findings

- Majorana boundary modes persist with large interchain tunneling
- Synthetic magnetic flux induces a robust leg-interchange symmetry
- The model is verified using DMRG and exact diagonalization

## Abstract

One promising avenue to study one-dimensional ($1$D) topological phases is to realize them in synthetic materials such as cold atomic gases. Intriguingly, it is possible to realize Majorana boundary modes in a $1$D number-conserving system consisting of two fermionic chains coupled only by pair-hopping processes. It is commonly believed that significant interchain single-particle tunneling necessarily destroys these Majorana modes, as it spoils the $\mathbb{Z}_2$ fermion parity symmetry that protects them. In this Letter, we present a new mechanism to overcome this obstacle, by piercing a (synthetic) magnetic $\pi$-flux through each plaquette of the Fermi ladder. Using bosonization, we show that in this case there exists an exact leg-interchange symmetry that is robust to interchain hopping, and acts as fermion parity at long wavelengths. We utilize density matrix renormalization group and exact diagonalization to verify that the resulting model exhibits Majorana boundary modes up to large single-particle tunnelings, comparable to the intrachain hopping strength. Our work highlights the unusual impacts of different topologically trivial band structures on these interaction-driven topological phases, and identifies a distinct route to stabilizing Majorana boundary modes in $1$D fermionic ladders.