For decades, scientists have been dedicated to detecting new particles that are not included in the standard model. A type of hypothetical ultralight scalars, such as axions or axion-like particles (ALPs), has attracted a lot of attention in a wide variety of research. Yet there has been no sensor that is small enough, or accurate enough to detect such particle.  

Recently, Prof. DU Jianfeng's group at the University of Science and Technology of China of Chinese Academy of Sciences developed a method that extends the investigation range deeper into smaller scales, that is, shorter than 20μm, which may lead to the detection of many more new particles. The findings were published in Nature Communications.

The solution proposed was to investigate the electron–nucleon monopole–dipole interactions. The researchers used a near-surface single electron spin which is a nitrogen-vacancy (NV) center in diamond, as the sensor. The NV center is less than 10 nm close to the surface of the diamond so that it allows close proximity between the electron and the nucleon. The sensor can then detect the electron–nucleon interaction between the NV center and the nucleons in a fused silica half-ball lens.  

As the experiment indicated, this new method may detect interactions at the force range as short as 0.1 μm. So far the researchers have found no clear evidence that proves the existence of new particle within its detection range, yet this method can be further improved to fit more studies concerning spin-related interactions. 

The reviewers highly recommended the results of the study as “compelling” and “could open the direct searchable window to larger masses of the interacting bosons”. According to the research group, this achievement may also inspire more discoveries in the fields including cosmology, quantum science and fundamental theories like the string theory.