Speaker
Description
Abstract. Two-photon transitions in a coherently prepared atomic medium support cooperative emission rates that scale as $N^{2}$, where $N$ is the number of emitters in the coherence volume. Because the two signal photons are emitted back-to-back, their momenta cancel and the Dicke phase-matching constraint met, so that the coherence volume can be made macroscopic. Together these features make such a medium a natural detector for ultralight dark sectors, whose small Standard Model couplings would otherwise restrict searches to narrow resonant haloscope or helioscope cavities.
Building on prior frameworks of Bhoonah, Bramante and Song, and others, I extend the construction into two new source classes. In the helioscope channels, solar dark photons and solar axions are converted to real photons either at a conducting plate (kinetic mixing $\chi$) or inside a magnetised bore (Primakoff $g_{a\gamma\gamma}$), and the resulting field seeds a broadband trigger in the coherently prepared sample. In the haloscope channels the same conversion is driven instead by the non-relativistic galactic halo and produces a narrowband stochastic trigger. The helioscope channels yield broadband sensitivity from sub-meV to eV-scale masses; the haloscope channels improve on existing dark-photon dark-matter constraints near the parahydrogen two-photon resonance at $\omega_{\mathrm{res}}\simeq 0.26~\mathrm{eV}$. I discuss the robustness of these projections, the regime in which the $N^{2}$ enhancement persists, and the implications for the CATCHY experimental program at Queen's University.