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arXiv · 2507.11051

Disorder-enabled directional delocalization and wave steering in time-modulated Dirac materials

Seulong Kim·Kihong Kim
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Abstract

We demonstrate a disorder-enabled yet localization-immune directional transport channel in time-modulated Dirac systems subject to stochastic temporal variations of a vector potential. In a spatially uniform medium, random temporal modulation induces strong Anderson localization for generic propagation directions, whereas waves propagating parallel to the modulation axis remain perfectly delocalized. This behavior originates from the pseudospin structure of the Dirac equation, which enforces exact suppression of interband coupling for specific propagation directions, thereby eliminating disorder-induced backscattering. As a result, temporal disorder acts as a symmetry-selective angular filter, producing highly collimated transport withoutspatial structuring. Unlike conventional impedance matching-based transmission in clean time-varying media, this mechanism arises intrinsically from stochastic temporal modulation and remains robust across a wide range of disorder models. These findings establish temporal disorder as a resource for direction-selective wave control, enabling reconfigurable beam steering, adaptive filtering, and disorder-tolerant nanophotonic components such as temporal beam shapers. More broadly, this phenomenon represents a temporal analogue of disorder-induced delocalization channels known in spatially disordered systems and demonstrates that randomness, typically associated with localization and transport suppression, can instead isolate aperfectly transmitting channel through symmetry-selective dynamics.

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Seulong Kim, Kihong Kim. 2025-07-15. Disorder-enabled directional delocalization and wave steering in time-modulated Dirac materials. https://doi.org/10.1002/nap2.70103

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