2D Topological Edge States in Periodic Space-Time Interfaces
Abstract
Topological edge states in systems of two (or more) dimensions offer scattering-free transport, exhibiting robustness to inhomogeneities and disorder. In a different domain, time-modulated systems, such as photonic time crystals (PTCs), offer non-resonant amplification drawing energy from the modulation. Combining these concepts, we explore topological systems that vary periodically in both time and space, manifesting the best of both worlds. We present topological phases and topological edge states in photonic space-time crystals - materials in which the refractive index varies periodically in both space and time, displaying bandgaps in both frequency and momentum. The topological nature of this system leads to topological invariants that govern the phase between refracted and reflected waves generated from both the spatial and the temporal interfaces. The 2D nature of this system leads to propagating edge states, and a unique edge state that grows exponentially in power whilst following the space-time edge.
Cite
@article{arxiv.2506.03986,
title = {2D Topological Edge States in Periodic Space-Time Interfaces},
author = {Ohad Segal and Yonatan Plotnik and Eran Lustig and Yonatan Sharabi and Moshe-Ishay Cohen and Alexander Dikopoltsev and Mordechai Segev},
journal= {arXiv preprint arXiv:2506.03986},
year = {2026}
}