Phase transition is one of cutting-edged subjects in the field of condensed matter physics, involving the existence and transformation of various physical states in the material world and regarded as the basic research domain for understanding the physical world. Phase transition in the general sense investigates the change of the macroscopic state of matter under the limit of thermodynamics. However, the recent research showed that the similar quantum phase transition still occurs in quantum Rabi model or its approximate version, J-C Model. Hence, current situation calls for further clarification of such a phenomenon.
In order to tackle such a problem, Prof. Luo Honggang and his team from School of Physical Science and Technology, LZU exerted their way into this field from 2013, together with Beijing Computational Science Research Center, Institute of Theoretical Physics of Chinese Academy of Sciences, CRN-SPIN Italy, University of Salerno and other academic units. Continuous progress has been made, such as ‘Mean photon number dependent variational method to the Rabi model’, ‘Ground-state phase diagram of the quantum Rabi model’, ‘Frequency-renormalized multipolaron expansion for the quantum Rabi model’ and so on.
Recently, they presented with the world the new advancements. By analysis and numerical method, they obtained the basic phase diagram, scaling function, critical index of the model and other physical quantities determining quantum phase transition universality. Meanwhile, they also obtained for the first time the universal, discontinuous scale function of the J-C model. In addition, the universality also extends to the case where the number of two levels N is greater than 1, ie, the Dicke model, indicating that the nature of the super-radiation phase transition found in the Dick model is the same as that of the quantum Rabi model, greatly promoting the understanding of the essential physics of such models. Related results were published in Physical Review Letters 119, 220601 (2017), and enjoyed the editor’s suggestion.
The work was funded by the National Natural Science Foundation of China (No.11604009, No.11574025, No.11325417, No.11674139, No.1121403), National Scholar Athletics Foundation of China (Grant No.U1530401) and the Future and Emerging Technologies (FET) program under FET-Open Grant No. 618083(CNTQC).
(Translated by Zhang Lu; proofread by Li Qi)
