Speaker
Description
The shape coexistence phenomenon is related with the presence in the same energy region of eigenstates with different deformations. Shape coexistence appears almost everywhere in the mass table, but its presence is specially remarkable in the Pt-Hg-Pb or in the Sr-Zr-Mo regions [1,2].
On the other hand, the concept of quantum phase transition (QPT), which has gained a lot of attention in nuclear physics, among other fields, during the last twenty five years, appears when the Hamiltonian that describes the quantum system can be written in terms of two pieces, at least, each one with a given symmetry, and a Hamiltonian parameter, i.e., a control parameter, allows to pass from one to the other symmetry. This passing supposes a sudden change in an order parameter and a discontinuity in the ground-state energy of the system or in some of its derivatives.
The goal of this talk is to try to clarify the connection between shape coexistence and QPT, two seemingly unrelated phenomena, but that, once studied in deep, share common aspects: the rapid change in the ground state structure when going through an isotope chain or the presence in the mean-field energy surface of several minima. To illustrate the similarities and differences between both phenomena, we will focus in the Zr and Sr region (including also Mo and Ru) which is known for the rapid change of the ground state deformation and also for the presence of intruder states coming from two-particle two-hole excitations across Z=40 shell closure [4,5,6]. Then we will move into the case of odd-even systems where we will study the Nb nuclei using the recently proposed intrinsic state formalism of the Interacting Boson Model with configurations mixing for odd systems [7,8]. This formalism allows to deal with two or more different configurations, with triaxial shapes and with single- or multiple-j shells.
[1] K. Heyde and J. L. Wood, "Shape coexistence in atomic nuclei", Rev. Mod. Phys. 83, 1467 (2011).
[2] P. E. Garrett, M. Zielińska, and E. Clément, "An experimental view on shape coexistence in nuclei", Prog. Part. Nucl. Phys. 124, 103931 (2022).
[4] J.E. García-Ramos and K. Heyde, "Subtle connection between shape coexistence and quantum phase transition: The Zr case", Phys. Rev. C 102, 054333-16p (2020).
[5] E. Maya-Barbecho and J.E. García-Ramos, "Shape coexistence in Sr isotopes", Phys. Rev. C 105, 034341 (2022).
[6] E. Maya-Barbecho, S. Baid, J. M. Arias, and J.E. García-Ramos, "At the borderline of shape coexistence: Mo and Ru", Phys. Rev. C 108, 034316 (2023).
[7] E. Maya-Barbecho and J.E. García-Ramos, "An intrinsic-state formalism for the Interacting Boson-Fermion Model with configuration mixing", Phys. Lett. B 868 (2025) 139724.
[8] E. Maya-Barbecho and J.E. García-Ramos, "An study of Nb isotopes using the intrinsic-state formalism of the interacting boson-fermion model with configuration mixing", under consideration in Phys. Rev. C.
| Contribution category | Theory |
|---|---|
| Presenter status | Faculty/Staff |