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arXiv · 2508.10726

Edge Reconstruction in a Quantum Spin Hall Insulator

Rahul Soni·Matthias Thamm·Gonzalo Alvarez·Bernd Rosenow·Adrian Del Maestro
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Abstract

We study interaction-driven edge reconstruction in a quantum spin Hall insulator described by the Bernevig-Hughes-Zhang model with Kanamori-Hubbard interactions using the real-space density matrix renormalization group method in both the grand-canonical and canonical ensembles. For a two-dimensional cylinder with a smooth edge, we identify discrete particle-number transitions that lead to a spin-polarized edge state stabilized by an emergent ferromagnetic exchange interaction. The reconstruction is orbital-selective, occurring predominantly in the $s$-orbital channel. Our results reveal a microscopic mechanism for emergent fluctuating moments at the edge that could compromise the topological protection of helical edge states by time reversal symmetry.

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Rahul Soni, Matthias Thamm, Gonzalo Alvarez, Bernd Rosenow, Adrian Del Maestro. 2025-08-14. Edge Reconstruction in a Quantum Spin Hall Insulator. https://doi.org/10.1103/98j3-424f

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