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arXiv · 2502.20918

Dynamics of transport by helical edge states

Luis Alberto Razo López·Pierre Wulles·Geoffroy J. Aubry·Sergey E. Skipetrov·Fabrice Mortessagne
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Abstract

Topologically nontrivial band structure of a material may give rise to special states that are confined to the material's boundary and protected against disorder and scattering. Quantum spin Hall effect (QSHE) is a paradigmatic example of phenomenon in which such states appear in the presence of time-reversal symmetry in two dimensions. Whereas the spatial structure of these helical edge states has been largely studied, their dynamic properties are much less understood. We design a microwave experiment mimicking QSHE and explore the spatiotemporal dynamics of unidirectional transport of optical angular momentum (or pseudospin) by edge states. Pseudospin-polarized signal propagation is shown to be immune to scattering by defects introduced along the edge. Its velocity is 2 to 3 orders of magnitude slower than the speed of light in the free space, which may have important consequences for practical applications of topological edge states in modern optical and quantum-information technologies.

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Luis Alberto Razo López, Pierre Wulles, Geoffroy J. Aubry, Sergey E. Skipetrov, Fabrice Mortessagne. 2025-12-05. Dynamics of transport by helical edge states. https://doi.org/10.1103/c6g6-4sgm

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