Shape evolution of ^72,74 Kr with temperature in covariant density functional theory

Abstract

The rich phenomena of deformations in neutron-deficient krypton isotopes such as the shape evolution with neutron number and the shape coexistence attract the interests of nuclear physicists for decades. It will be interesting to study such shape phenomena using a novel way, i.e., by thermally exciting the nucleus. So in this work, we develop the finite temperature covariant density functional theory for axially deformed nuclei with the treatment of pairing correlations by BCS approach, and apply this approach for the study of shape evolutions in 72,74 Kr with increasing temperatures. For 72 Kr, with temperature increasing, the nucleus firstly experiences a relatively quick weakening in oblate deformation at temperature T ∼ 0.9 MeV, and then changes from oblate to spherical at T ∼ 2.1 MeV. For 74 Kr, its global minimum locates at quadroupole deformation β2 ∼ −0.14 and abruptly changes to spherical at T ∼ 1.7 MeV. The proton pairing transition occurs at critical temperature 0.6 MeV following the rule Tc = 0.6∆p(0) where ∆p(0) is the proton pairing gap at zero temperature. The signatures of the above pairing transition and shape changes can be found in the curve of the specific heat. The single-particle level evolutions with the temperature are presented.

Shape transition with temperature of the pear-shaped nuclei in covariant density functional theory

“…[13] where the BCS limit of finite-temperature HartreeFock Bogoliubov equations is derived, we obtain the finite-temperature RMF + BCS equation. The finite-temperature Dirac equation for single nucleons reads [38] [γ µ (i∂…”

Shell corrections with finite temperature covariant density functional theory *

“…Later, the finite temperature Hartree-Fock approximation [39][40][41] and the finite temperature Hartree-Fock-Bogoliubov theory [42] Er and rare-earth nuclei using the relativistic Hartree-BCS theory [43,44]. In recent years, the finite temperature relativistic Hartree-Bogoliubov theory [45] and relativistic Hartree-Fock-Bogoliubov theory [46] for spherical nuclei were developed and employed in studies in which the relations between the critical temperature for the pairing transition and pairing gap at zero temperature are explored. Following the BCS limit of the HFB theory [42], in 2017, we developed a finite-temperature covariant density functional theory for an axial-deformed space and studied the shape evolution of Kr [47].…”

Continuum Skyrme-Hartree-Fock-Bogoliubov theory with Green's function method for odd- A nuclei

“…[66,67], the fully self-consistent relativistic continuum random-phase-approximation (RCRPA) was developed with the Green's function of the Dirac equation and used to study the contribution of the continuum to nuclear collective excitations. In 2014, considering the great successes of the covariant density functional theory (CDFT) [31,[68][69][70][71][72][73][74][75][76][77][78][79], the authors developed the continuum CDFT based on the GF method, with which the accurate energies and widths of the single-neutron resonant states were calculated for the first time [80]. This method has been further extended to describe single-particle resonances for protons [81] and Λ hyperons [82].…”