# Emergent bosons in the fermionic two-leg flux ladder

## TL;DR

This paper investigates how fermionic particles in a two-leg flux ladder system can form bosonic pairs under certain interactions, leading to a phase transition from vortex density waves to charge density waves, demonstrated through DMRG simulations.

## Contribution

It reveals the emergence of bosonic behavior from fermionic systems in a flux ladder, highlighting a flux-induced quantum phase transition.

## Key findings

- Fermions form tightly bound pairs acting as bosons under specific interactions.
- A flux-induced quantum phase transition from vortex density wave to charge density wave.
- Numerical evidence of bosonic-like phases in a fermionic flux ladder.

## Abstract

We study the emergence of bosonic pairs in a system of two coupled one-dimensional fermionic chains subject to a gauge flux (two-leg flux ladder), with both attractive and repulsive interaction. In the presence of strong attractive nearest-neighbor interaction and repulsive next-to-nearest-neighbor interaction, the system crosses into a regime in which fermions form tightly bound pairs, which behave as bosonic entities. By means of numerical simulations based on the density-matrix-renormalization-group (DMRG) method, we show in particular that in the strongly paired regime, the gauge flux induces a quantum phase transition of the Ising type from vortex density wave (VDW) to a charge density wave (CDW), characteristic of bosonic systems.