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.
@article{arxiv.2502.20918,
title = {Dynamics of transport by helical edge states},
author = {Luis Alberto Razo López and Pierre Wulles and Geoffroy J. Aubry and Sergey E. Skipetrov and Fabrice Mortessagne},
journal= {arXiv preprint arXiv:2502.20918},
year = {2025}
}
Comments
6 Pages, 4 figures, Supplemental Material included at the end