Robustness of discrete semifluxons in closed Bose-Hubbard chains

TL;DR

This paper investigates how atom interactions influence the ground state and excitations of Bose-Hubbard chains with variable geometry and twisted links, revealing enhanced semifluxon superpositions near the pi-flux point.

Contribution

It provides a detailed analysis of the ground state and low-energy excitations of Bose-Hubbard chains with tunable geometry and flux, highlighting the role of interactions in semifluxon formation.

Findings

Interactions promote strongly correlated semifluxon superpositions.

Energy spectrum analyzed via diagonalization and Bogoliubov--de Gennes equations.

System exhibits behavior akin to an interacting gas of semifluxons near pi-flux.

Abstract

We present the properties of the ground state and low-energy excitations of Bose-Hubbard chains with a geometry that varies from open to closed and with a tunable twisted link. In the vicinity of the symmetric $\pi-$flux case the system behaves as an interacting gas of discrete semifluxons for finite chains and interactions in the Josephson regime. The energy spectrum of the system is studied by direct diagonalization and by solving the corresponding Bogoliubov--de Gennes equations. The atom-atom interactions are found to enhance the presence of strongly correlated macroscopic superpositions of semifluxons.