A group led by Academician GUO Guangcan from University of Science and Technology of China (USTC) of the Chinese Academy of Sciences, collaborating with Prof. Charles Adams from Durham University, have carried out an experimental simulation of many-body self-organization based on Rydberg Atoms. The results were published on April 29 in Physics Review X. 

There are many phenomena in nature following the evolutionary laws of many-body physics, which obey a kind of self-organization law. An interesting and important phenomenon is the self-organized criticality (SOC) behavior: a system is attracted to a critical point at which the behavior of the system changes dramatically, such as forest fires and the spread of viruses. Therefore, the study of SOC is of great significance to simulate the complex many-body problem in nature.  

The atoms in the Rydberg Atom are much more strongly interacting with each other than with the atomic gas, and the high polarizability allows the dipole interactions between the atoms to be in the range of several microns long. The strong interaction enables us to observe the non-equilibrium phase transition in the ensemble.  

The accuracy of traditional method used to detect non-equilibrium phase transitions is only in the order of several hundred MHz. The researchers in this study have proposed a new method by using the electromagnetically induced transparency effect of the Rydberg Atom. Compared with the traditional method, the frequency resolution is improved by two orders of magnitude.  

They measured the complete phase diagram, observed the dynamic behavior near the critical point, and revealed previously unobserved optical response and time-domain spectral properties in non-equilibrium dynamics under weakly driven light. 

It is found that when the average number of Rydberg Atom in an interaction reaches a critical value, the system will transition from non-interacting phase to interacting-phase and vice versa.