Ab Initio Multi-Reference In-Medium Similarity Renormalization Group Calculations of Even Calcium and Nickel Isotopes

TL;DR

This paper applies a new multi-reference in-medium similarity renormalization group method to study calcium and nickel isotopes, analyzing ground states and neutron separation energies with chiral interactions, and discusses the importance of three-nucleon forces.

Contribution

It introduces the Multi-Reference In-Medium Similarity Renormalization Group approach for isotopic calculations, emphasizing the role of chiral three-nucleon interactions.

Findings

Excellent agreement with Coupled Cluster results at shell closures.

Chiral 3N interactions are crucial for accurate energy trends.

Identifies deficiencies in current Hamiltonians for future improvements.

Abstract

We use the newly developed Multi-Reference In-Medium Similarity Renormalization Group to study all even isotopes of the calcium and nickel isotopic chains, based on two- plus three-nucleon interactions derived from chiral effective field theory. We present results for ground-state and two-neutron separation energies and quantify their theoretical uncertainties. At shell closures, we find excellent agreement with Coupled Cluster results obtained with the same Hamiltonians. Our results highlight the importance of the chiral 3N interaction to obtain a correct reproduction of experimental energy trends, and their subtle impact on the location of the neutron drip lines in the Ca and Ni chains. At the same time, we uncover and discuss deficiencies of the input Hamiltonians which need to be addressed by the next generation of chiral interactions.