Wave-like Dark Matter and Axions

Abstract

Despite composing 85% of the matter in the universe, the exact nature of dark matter is still unknown. The possibility of wave-like dark matter and axions is driving a surge of new experiments that are vitalized by progress in quantum amplification and optics, microwave electronics, high magnetic fields, and cryogenics. We discuss the technology that enables such searches, and break down the experiments by their reliance on different axion couplings. We explain how the Axion Dark Matter eXperiment (ADMX) has achieved sensitivity to a particularly compelling class of dark matter candidates, known as DFSZ axions, in a narrow range of axion masses. Finally, with a new fleet of experiments arriving online, we present their goals to probe as yet unexplored parts of axion parameter space in the coming years.