Excited-state Quantum Phase Transitions In The Interacting Boson Model

The quantum phase transitions of the excited-states with L~?=0~+ in the interacting boson model are systematically investigated by adopting the coherent state technique and IBAR numerical program.In the U(5)-SO(6)transitional region and the U(5)-SU(3),SU(3)-SO(6)transitional region,by comparing their excited-state quantum phase transition characteristics,it is found that various types of excited-state quantum phase transitions may widely occur in the model as functions of excitation energy.In addition,the separatrix in energy spectra as a function of the corresponding control parameter has been derived in the large-N limit,and the d-boson occupation probability has been applied to identify these excited-state quantum phase transitions,which indicates that the phase diagram of the interacting boson model can be dynamically extended along the direction of excitation energy.Finally,the underlying relation between the excited-state quantum phase transition and the chaotic dynamics is briefly discussed.