Many-body quantum muon effects and quadrupolar coupling in solids
In collaboration with researchers from the United Kingdom, from Durham University and the Rutherford Appleton Laboratory, we have published a paper on the quantum effects of muons. While quantum effects of atomic nuclei, such as quantum uncertainty in their position, quantum tunnelling, and entanglement, are known to strongly affect the structure and dynamics of many materials, similar quantum effects of muons, which we studied, can severely alter the interpretation of powerful muon spin relaxation measurements. In our paper, we develop a unified description of quantum effects of light particles (muons and nuclei) in materials, clarifying the role of many-body quantum entanglement and anharmonicity in determining their behaviour. As a first proof of concept, we have applied and tested these insights against our precision muon quadrupolar level-crossing measurements on solid nitrogen. This allowed to improve the accuracy of an important constant of this material: its nuclear quadrupolar coupling constant, by almost 3× compared to all previous attempts. This represents the first improvement in the accuracy of this constant in over 45 years.
Our study was also selected for an invited contribution to the Nature Portfolio and Springer Nature Communities. In it, we introduce the main concepts behind our paper to the general audience. You can find it here: https://physicscommunity.nature.com/posts/quantum-muon-effects-in-solids
The full text of the original paper can be found here: https://www.nature.com/articles/s42005-023-01260-7