Excited-state Quantum Phase Transitions In The Finite Boson System

In the framework of the interacting boson model(IBM),the excited-state quantum phase transitions(ESQPTs)in the finite boson system have been systematically investigated.On the one hand,the functional relation between the control parameters and the critical energy of the ESQPTs in the transitional regions including U(5)-SO(3),U(5)-SU(3)and SU(3)-SU(3)have been analyzed in the mean-field level by using the coherent state method.On the other hand,the program IBAR is employed to solve the eigenvalue equation for a given IBM Hamiltonian,by which the effects of angular momentum on the ESQPTs in the model with a realistic number of boson(N=15)have been studied.Specifically,the d boson occupation probabilities for L=0,L=4 and L=10 states in each transitional region have been calculated as functions of excitation energy.Besides,the typical energy ratios and momentum of inertia in the 1st order phase transitional regions have been also analyzed.The results indicate that the ESQPTs in the IBM are robust even for a realistic number of boson comparable to nuclear system,while the features of ESQPTs become weak with increasing of angular momentum.The present analysis provide a theoretical basis for searching for ESQPTs in nuclei.