The cobalt-based honeycomb magnet BaCo2(AsO4)2 (BCAO) has recently emerged as a promising platform for frustrated magnetism beyond conventional paradigms. Neutron-scattering experiments and first-principles calculations have revealed an unexpected double-zigzag (dZZ) magnetically ordered ground state, whose microscopic origin remains under active debate. Here, we revisit this problem within a ferro--antiferromagnetic J1--J3 Heisenberg model on the honeycomb lattice using a generalized Schwinger-boson mean-field theory (gSBMFT) that treats ferromagnetic and antiferromagnetic interactions on equal footing. This approach, combined with exact diagonalization (ED), allows us to demonstrate the emergence of the dZZ phase in a narrow parameter range, stabilized by quantum fluctuations through an order-by-disorder mechanism, in good agreement with recent density-matrix renormalization-group (DMRG) results. We further characterize the associated magnetic excitations and discuss their relevance to recent inelastic neutron-scattering (INS) measurements on BCAO.
@article{arxiv.2511.16429,
title = {Order-by-disorder from Schwinger bosons in a frustrated honeycomb ferromagnet},
author = {Arnaud Ralko and Jaime Merino},
journal= {arXiv preprint arXiv:2511.16429},
year = {2026}
}