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arXiv · 2610.04684

Electron-phonon control of obstructed and quantum spin Hall topology in an altermagnet

Kuntal Bhattacharyya·Bilal Tanatar·Saurabh Basu
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Abstract

We theoretically demonstrate control over the interplay between obstructed atomic insulating and first-order topological phases via electron-phonon coupling (EPC) in a $d$-wave altermagnet (AM) that hosts nonrelativistic spin-split bands with zero net magnetization. By embedding a $d_{x^{2}-y^{2}}$-wave AM in a quantum spin Hall (QSH) insulator, we show that an altermagnetic order beyond a critical strength reconstructs the parent QSH state of a Bernevig-Hughes-Zhang (BHZ)-type topological insulator (TI) into an obstructed atomic insulator (OAI), characterized by nontrivial bulk polarization with quantized fractional corner charges, accompanied by characteristic in-gap boundary states, while the spin Chern number vanishes. Upon incorporating sufficiently strong EPC, the polaronic dressing reorganizes the Wannier centers and the associated effective edge topology, thereby weakening the altermagnetism-induced OAI phase and restoring the helical QSH edge modes. Further, EPC eventually drives the system into a trivial insulator. By uncovering a controllable switching mechanism between topologically distinct insulating phases in AMs, our study establishes a direct route toward phonon-tuned spintronic functionalities in unconventional magnetic platforms.

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Kuntal Bhattacharyya, Bilal Tanatar, Saurabh Basu. 2026-10-03. Electron-phonon control of obstructed and quantum spin Hall topology in an altermagnet. https://arxiv.org/abs/2610.04684

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