Jacobi-type transitions in the interacting boson model

Abstract

We examine, within the framework of the interacting boson model, the structural evolution along the excitation energy across the saddle points of potential wells in a finite nuclear system, and its connection with excited-state quantum phase transitions (ESQPTs). We find that transitions between $\ensuremath{\gamma}$-rigid and $\ensuremath{\gamma}$-soft shapes occur as a function of angular momentum, $L$, analogous to the Jacobi transitions occurring in rotating stars. Empirical evidence of these transitions is found in the rotational spectra of $^{156--162}\mathrm{Gd}$.