Exotic neutron-rich medium-mass nuclei with realistic nuclear forces

TL;DR

This paper introduces a new theoretical approach to accurately model exotic neutron-rich medium-mass nuclei, successfully describing their properties without fitted interactions and clarifying shell evolution mechanisms.

Contribution

The study applies the EKK theory with realistic nuclear forces to shell-model calculations, enabling first-principles descriptions of exotic nuclei in the $sd$+$pf$ shells.

Findings

Accurately describes energies, E2 properties, and spectroscopic factors of neutron-rich isotopes.

Provides the first shell-model description of the island of inversion without fitted interactions.

Clarifies particle-hole excitations across the $sd$-$pf$ magic gap.

Abstract

We present the first application of the newly developed EKK theory of the effective nucleon-nucleon interaction to shell-model studies of exotic nuclei, including those where conventional approaches with fitted interactions encounter difficulties. This EKK theory enables us to derive the interaction suitable for several major shells ($sd$+$pf$ in this work). By using such an effective interaction obtained from the Entem-Machleidt QCD-based $\chi\mathrm{N}^3\mathrm{LO}$ interaction and the Fujita-Miyazawa three-body force, the energies, E2 properties and spectroscopic factors of low-lying states of neutron-rich Ne, Mg and Si isotopes are nicely described, as the first shell-model description of the "island of inversion" without fit of the interaction. The long-standing question as to how particle-hole excitations occur across the $sd$-$pf$ magic gap is clarified with distinct differences from the conventional approaches. The shell evolution is shown to appear similarly to earlier studies.