Relativistic Hartree-Fock model for axial-symmetric nuclei with quadruple and octupole deformations

TL;DR

This paper introduces the OD-RHF model for studying octupole-deformed nuclei, demonstrating its reliability through analysis of $^{144}$Ba and highlighting the importance of Fock terms and tensor forces in stabilizing octupole deformation.

Contribution

The paper develops the OD-RHF model for axial-symmetric octupole nuclei and verifies its effectiveness using $^{144}$Ba with various RHF Lagrangians, emphasizing the role of Fock terms and tensor forces.

Findings

The OD-RHF model reliably describes octupole nuclei.

Octupole deformation in $^{144}$Ba is influenced by neutron and proton intruder components.

Fock terms and tensor forces are crucial in stabilizing octupole deformation.

Abstract

\textbf{Background:} The initial observation of a negative-parity state in proximity to the ground state in the 1950s marked the advent of extensive research into octupole deformed nuclei. Since then, the physics of octupole deformed nuclei has consistently held a special interest within the field of nuclear physics. In the present era, with the advent of sophisticated radioactive ion beam (RIB) facilities and advanced detectors, coupled with the remarkable capabilities of high-performance computing, extensive and intensive explorations are being conducted from both experimental and theoretical perspectives to elucidate the physics of octupole deformed nuclei. \textbf{Results:} This work establishes the OD-RHF model, which provides a reliable tool for studying octupole nuclei over a fairly wide range. The reliability of the newly developed OD-RHF model is illustrated by taking the octupole nucleus $^{144}$Ba as an example. Furthermore, the octupole deformation effects in $^{144}$Ba is verified by using the RHF Lagrangians PKO$i$ ($i=1,2,3$) and the RMF one DD-ME2. The intrusion of the neutron $1i_{13/2}$ and proton $1h_{11/2}$ components is demonstrated to play an essential role in determining the notable octupole deformation of $^{144}$Ba using PKO$i$ ($i=1,2,3$) and DD-ME2. It is indicated that the Fock terms play an important role in stabilizing the octupole deformation. More specifically, due to the repulsive tensor coupling between the intrude components and the core of $^{144}$Ba, the tensor force component carried by the $\pi$-PV coupling, that contributes only via the Fock terms, plays an opposing role in the formation of the octupole deformation of $^{144}$Ba.