Emergence of the unexpected charge-density-wave phase driven by artificial gauge field in three-leg Bose-Hubbard ladder

TL;DR

This study reveals the unexpected emergence of charge-density-wave phases in a three-leg Bose-Hubbard ladder under artificial gauge fields, highlighting complex phase transitions and competition between vortex and density-wave orders.

Contribution

It uncovers novel charge-density-wave phases induced by artificial gauge fields in a bosonic ladder system, expanding understanding of quantum phase behavior under synthetic gauge fields.

Findings

Charge-density-wave phases appear in flux regimes with only on-site interactions.

Reentrant quantum phase transitions between CDW and vortex-superfluid phases.

Identification of an isolated CDW region not explained by strong-coupling limits.

Abstract

We investigate hard-core bosons at half filling on a three-leg ladder under the uniform artificial gauge field. By analyzing current patterns and correlation functions, we uncover a rich quantum phase diagram containing multiple superfluid and insulating phases. In bosonic ladder systems, increasing the gauge flux typically destabilizes the Meissner phase and leads to vortex phases characterized by circulating currents. In the present system, however, we find that charge-density-wave (CDW) phases emerge precisely in such a flux regime despite the presence of only an on-site interaction, where vortex states are naturally expected and are indeed realized in nearby parameter regions. While part of this behavior can be qualitatively understood from a strong-coupling perspective, we also identify an isolated CDW region that cannot be connected to such limits. Furthermore, upon increasing the artificial gauge flux, we observe a reentrant sequence of quantum phase transitions, CDW $\to$ vortex-superfluid $\to$ CDW, revealing a strong competition between the vortex phase and the density-wave order.