Dynamic Topological Metasurfaces via Moving Exceptional Points for Terahertz Wavefront Engineering

ABSTRACT Topological metasurfaces are a reliable platform for wavefront engineering using geometric phases from Exceptional Points (EPs). However, current implementations rely on static structural parameters, confining topological singularity to fixed coordinates and limiting active functionality. While recent mechanical tuning approaches show dynamic non‐Hermitian control, achieving mode switching between different spatial regimes remains a challenge. Here, we propose and experimentally demonstrate a reconfigurable topological metasurface in the terahertz regime that leverages the phase transition of Ge 2 Sb 2 Te 5 (GST) to drive a deterministic migration of the EP. We find that the amorphous to crystalline transition induces a discrete reconstruction of the radiation continuum boundaries, switching between transmissive and reflective environments, thereby fundamentally altering the system's coupling matrix. By synergizing this mobile topological phase with the orientation‐dependent Pancharatnam‐Berry (PB) phase, we implement a spin‐decoupled, active wavefront manipulation scheme on a flexible, substrate‐free platform. The device dynamically switches the left‐circularly polarized channel from a near‐field plasmonic metalens to a far‐field orbital angular momentum (OAM) generator (), while maintaining a topologically trivial, stable response for the RCP polarization. This research bridges the gap between active non‐Hermitian physics and integrated terahertz photonics, and paves the way for adaptive sensing and 6G communication systems.