Large-$N$ SU(4) Schwinger boson theory for coupled-dimer antiferromagnets
Abstract
We develop a systematic large- expansion based on the Schwinger boson representation of SU(4) coherent states of dimers for the paradigmatic spin- bilayer square lattice Heisenberg antiferromagnet. This system exhibits a quantum phase transition between a quantum paramagnetic state and a N\'eel order state, driven by the coupling constant , which is defined as the ratio between the inter-dimer and intra-dimer exchange interactions. We demonstrate that this approach accurately describes static and dynamic properties on both sides of the quantum phase transition. The critical coupling constant and the dynamic spin structure factor reproduce quantum Monte Carlo results with high precision. Notably, the corrections reveal the longitudinal mode of the magnetically ordered phase along with the overdamping caused by its decay into the two-magnon continuum. The present large- Schwinger boson theory can be extended to more general cases of quantum paramagnets that undergo a quantum phase transition into magnetically ordered states.
Keywords
Cite
@article{arxiv.2409.04627,
title = {Large-$N$ SU(4) Schwinger boson theory for coupled-dimer antiferromagnets},
author = {Shang-Shun Zhang and Yasuyuki Kato and E. A. Ghioldi and L. O. Manuel and A. E. Trumper and Cristian D. Batista},
journal= {arXiv preprint arXiv:2409.04627},
year = {2025}
}