Using a recently developed spin-based amplifier, scientists from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences contained hypothetical axions within the axion window.
Searches for axion and axionlike particles may be the key to unlocking some of the most profound puzzles about our Universe, such as dark matter and energy. Some hypotheses predicted the mass of axions probably lies within the well-motivated “axion window” (0.01 meV-1 meV). However, existing laboratory searches and astrophysical observation mostly search for the axions outside the axion window.
The exchange of axions between fermions results in an exotic dipole-dipole interaction that may be detectable by laboratory experiments. In this new study, scientists searched for an exotic dipole-dipole interaction between polarized electron and neutron spins.
They used a large collection of polarized rubidium-87 electrons and polarized Xeon-129 nuclear spins as two kinds of fermions.
Rubidium could produce an unusual signal on the Xeon nuclear spins due to the exchange of axions. The polarised Xeon-129 nuclear spins are then utilized to search for the signal resonantly.
The scientists specifically demonstrated how the long-lived Xeon-129 spins function as a quantum preamplifier, which can enhance the exotic signal by a factor of more than 40. With this method, they were able to offer stringent constraints on axion-mediated neutron-electron coupling for the axion mass range of 0.03 meV to 1 meV within the axion window.
Prof. PENG Xinhua from USTC, who led the study, said, “The research offers a sensitive quantum technique to realize the indirect axion searches with a recently-developed spin-based amplifier. As a new implementation, the spin-based amplifier scheme extends the capabilities of spin measurements. It can be further applied to resonantly search for hypothetical particles beyond the Standard Model, such as new spin-1 dark photons.”