Role of triaxiality in Ge-76 and Se-76 nuclei studied with Gogny energy density functionals

The structure of the nuclei Ge-76 and Se-76 is studied with symmetry conserving configuration mixing methods based on the Gogny D1S interaction. These two nuclei are of key importance in the search for neutrinoless double-beta decay. The energy density functionals used here include symmetry restorations (particle number and angular momentum) and shape mixing within the generator coordinate method. The comparison with the experimental data shows a good qualitative agreement when triaxial shapes are included, revealing the important role played by this degree of freedom in these two nuclei.