English

Boundary topological orders of (4+1)d fermionic $\mathbb{Z}_{2N}^{\mathrm{F}}$ SPT states

Strongly Correlated Electrons 2026-03-09 v2 High Energy Physics - Phenomenology High Energy Physics - Theory

Abstract

We investigate (3+1)d topological orders in fermionic systems with an anomalous Z2NF\mathbb{Z}_{2N}^{\mathrm{F}} symmetry, where its Z2F\mathbb{Z}_2^{\mathrm{F}} subgroup is the fermion parity. Such an anomalous symmetry arises as the discrete subgroup of the chiral U(1) symmetry of ν\nu copies of Weyl fermions of the same chirality. Inspired by the crystalline correspondence principle, we deform the anomalous Z2NF\mathbb{Z}_{2N}^\mathrm{F} symmetry of (3+1)d Weyl fermion to the anomalous CN×Z2FC_N \times \mathbb{Z}_2^\mathrm{F} symmetry. Then we microscopically construct symmetry-preserving gapped boundary states of the closely-related (4+1)d CN×Z2FC_N\times \mathbb{Z}_2^{\mathrm{F}} symmetry-protected topological (SPT) state (with CNC_N being the NN-fold rotation), whenever it is possible. In particular, for ν=N\nu=N, we show that the (3+1)d symmetric gapped state admits a topological Z4\mathbb{Z}_4 gauge theory description at low energy, and propose that a similar theory saturates the corresponding Z2NF\mathbb{Z}_{2N}^\mathrm{F} anomaly. For NνN \nmid \nu, our construction admits no topological quantum field theory (TQFT) symmetric gapped state; while for ν=N/2\nu=N/2, we find a non-TQFT symmetric gapped state via stacking lower-dimensional (2+1)d non-discrete-gauge-theory topological order inhomogeneously. For other values of ν\nu, no symmetric gapped state is possible within our construction, which is consistent with the no-go theorem by Cordova-Ohmori.

Keywords

Cite

@article{arxiv.2411.05786,
  title  = {Boundary topological orders of (4+1)d fermionic $\mathbb{Z}_{2N}^{\mathrm{F}}$ SPT states},
  author = {Meng Cheng and Juven Wang and Xinping Yang},
  journal= {arXiv preprint arXiv:2411.05786},
  year   = {2026}
}

Comments

16 pages, 3 figures