Author(s): Yoan Spahn, Jens Hartmann, Benedikt Saalfrank, Michael Fleischhauer, Thomas Halfmann, and Thorsten Peters We report the experimental observation of motion-induced directionality in collective atomic emission within a hollow-core waveguide, establishing a general principle: directional interactions can emerge from collective phase engineering alone. Remarkably, neither single-emitter asymmetry nor any as… [Phys. Rev. Lett. 137, 123601] Published Mon Sep 14, 2026