Dynamical spin correlations in kagome antiferromagnets: Comparison of the Abrikosov fermion and Schwinger boson approaches beyond mean field
Phys. Rev. B 114, 074405 – Published 5 August, 2026
DOI: https://doi.org/10.1103/h85g-v6zx
Abstract
Quantum spin liquids exhibit fractionalized spin excitations as a consequence of strong quantum many-body effects and have therefore attracted considerable attention. The kagome antiferromagnetic Heisenberg model is a promising candidate for realizing a quantum spin-liquid ground state; however, the nature of its excitation spectrum remains controversial, particularly for the presence of a spin gap and the gauge structure coupled to fractional quasiparticles. To address these issues, parton approaches have been extensively employed in theoretical studies, where spin operators are represented in terms of either fermionic or bosonic quasiparticles; the former approach is known as the Abrikosov fermion method, while the latter is referred to as the Schwinger boson method. Thus far, these approaches have been pursued independently, and it has remained unclear how the results obtained from these two different frameworks compare with each other, particularly with respect to the spin dynamics and gauge structure of the kagome antiferromagnet. Here, we investigate the dynamical spin structure factor of the antiferromagnetic Heisenberg model with a Dzyaloshinskii-Moriya interaction on a kagome lattice, which is relevant to the material herbertsmithite, by employing both the Abrikosov fermion and Schwinger boson approaches. We find that the dynamical spin structure factor obtained from the Abrikosov fermion mean-field theory exhibits dome-shaped features, and that its continuum structure significantly depends on the gauge structure of the spin-liquid Ansatz. On the other hand, the Schwinger boson mean-field theory yields a concave-down structure in the low-energy region of the dynamical spin structure factor, which is distinct from that obtained using the Abrikosov fermion approach. Moreover, the low-energy gap is substantially reduced, and the low-energy spectral weight is enhanced, by incorporating many-body effects beyond the mean-field approximation, which is consistent with experimental observations. Our results suggest the importance of many-body effects in the Schwinger boson theory for capturing the low-energy spin dynamics of kagome antiferromagnets.
