Analytical approach to a bosonic ladder subject to a magnetic field

TL;DR

This paper uses a low-energy field theory to analyze a bosonic two-leg ladder under magnetic flux, revealing local density/current patterns, chiral-current reversal mechanisms, and effects of rung interactions.

Contribution

It introduces a formalism that explains symmetry breaking, current reversal, and interaction effects in bosonic ladders with magnetic flux, extending understanding of these quantum systems.

Findings

Local density and current patterns due to symmetry breaking

Chiral-current reversal caused by competing current components

Nearest-neighbor rung interactions favor population imbalance

Abstract

We examine a bosonic two-leg ladder model subject to a magnetic flux, and especially focus on a regime where the lower energy band has two minima. By using a low-energy field theory approach, we study several issues discussed in the system: the existence of local patterns in density and current, chiral-current reversal, and the effect of a nearest-neighbor interaction along the rung direction. In our formalism, the local patterns are interpreted as a result of breaking of discrete symmetry. The chiral-current reversal occurs through a competition between a current component determined at a commensurate vortex density causing an enlargement of the unit cell, and another component, which is proportional to the magnetic field doping from the corresponding commensurate flux. The nearest-neighbor interaction along the rung direction available with the technique on a synthetic dimension is shown to favor a population-imbalance solution in an experimentally relevant regime.