Nature of the bosonic edge phase in a double quantum spin Hall insulator
Abstract
Field-theoretic analysis has predicted that the edge of a double quantum spin Hall insulator (DQSHI) can undergo an interaction-driven transition from a phase with fermionic edge modes into one with only bosonic modes. All single-fermion edge excitations are gapped in this bosonic edge phase, but fermion pairs remain gapless, leading to distinct experimental signatures. We numerically simulate the interacting DQSHI edge and verify the existence of the bosonic edge phase. This calculation requires an explicit bulk embedding of the DQSHI edge, due to its mixed anomaly between charge and Sz conservation. We hence employ segment DMRG on an infinite two-dimensional cylinder, where the DQSHI bulk is modeled in terms of two copies of the spin-up lowest Landau level, combined with their time-reversed counterparts. We find that interactions can open a single-fermion gap at the DQSHI edge while fermion pairs remain gapless, matching the predictions for the bosonic edge phase. We find the scaling of the single-fermion gap with interaction strength to be consistent with field-theoretic calculations, and discuss the relevance of the bosonic edge phase to twisted homobilayers of WSe2 and MoTe2. We elaborate on the methodological extension of the segment geometry used here to other topological phases with edge anomalies.
Related
- Haldane-Holstein model at fractional filling: Route to bosonic fractional Chern insulator and quantum anomalous Hall crystal
- Quantum Noise Limited Nonlinear Phase-Preserving Amplification of a Bosonic Mode
- Symplectic Hopf Insulator: Delicate Topology in Bosonic Bogoliubov-de Gennes Systems
- Quantum resource trade-offs of mixed sparse single and double factorization for qubitization-based phase estimation
- Nonreciprocal Floquet tunneling dynamics of spin-orbit-coupled bosonic atoms in a non-Hermitian double-well potential
BibTeX
@misc{feuerpfeil2026nature,
title = {{Nature of the bosonic edge phase in a double quantum spin Hall insulator}},
author = {Andreas Feuerpfeil and Ronny Thomale and Trithep Devakul and Nicolas Regnault and Julian May-Mann},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.30251},
eprint = {2610.30251},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.30251},
}
RIS
TY - UNPB
TI - Nature of the bosonic edge phase in a double quantum spin Hall insulator
AU - Andreas Feuerpfeil
AU - Ronny Thomale
AU - Trithep Devakul
AU - Nicolas Regnault
AU - Julian May-Mann
PY - 2026
DA - 2026/10/21
PB - arXiv
DO - 10.48550/arxiv.2610.30251
UR - https://arxiv.org/abs/2610.30251
AB - Field-theoretic analysis has predicted that the edge of a double quantum spin Hall insulator (DQSHI) can undergo an interaction-driven transition from a phase with fermionic edge modes into one with only bosonic modes. All single-fermion edge excitations are gapped in this bosonic edge phase, but fermion pairs remain gapless, leading to distinct experimental signatures. We numerically simulate the interacting DQSHI edge and verify the existence of the bosonic edge phase. This calculation requires an explicit bulk embedding of the DQSHI edge, due to its mixed anomaly between charge and S^z conservation. We hence employ segment DMRG on an infinite two-dimensional cylinder, where the DQSHI bulk is modeled in terms of two copies of the spin-up lowest Landau level, combined with their time-reversed counterparts. We find that interactions can open a single-fermion gap at the DQSHI edge while fermion pairs remain gapless, matching the predictions for the bosonic edge phase. We find the scaling of the single-fermion gap with interaction strength to be consistent with field-theoretic calculations, and discuss the relevance of the bosonic edge phase to twisted homobilayers of WSe_2 and MoTe_2. We elaborate on the methodological extension of the segment geometry used here to other topological phases with edge anomalies.
ER -