Quantum Spin Hall Effect with Extended Topologically Protected Features in Altermagnetic Multilayers.
basic_science · Level V
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- Record sourced from PubMed, PMID 41849241.
- Also identified by DOI 10.1021/acs.nanolett.6c00136.
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Abstract
Conventional topological classification dictates that time-reversal symmetry confines the quantum spin Hall (QSH) effect to a <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msub></math> classification, permitting only a single pair of gapless helical edge states. Here, we utilize altermagnetism to circumvent this fundamental constraint. We demonstrate a unique QSH phase possessing multiple pairs of gapless helical edge states in altermagnetic multilayers. This QSH phase, characterized by a mirror-spin Chern number, emerges from the interplay of spin-orbit coupling and <i>d</i>-wave altermagnetic ordering. Moreover, using first-principles calculations, we identify altermagnetic Fe<sub>2</sub>Se<sub>2</sub>O multilayers as promising material candidates, in which the number of gapless helical edge states scales with the number of layers, leading to a large, exactly quantized, and experimentally accessible spin-Hall conductance. Our findings unveil a new mechanism for stabilizing multiple pairs of gapless helical edge states, expanding the scope of QSH effects, and providing a blueprint for utilizing altermagnetism to engineer topological phases.