Tensor-force-driven Jahn-Teller effect and shape transitions in exotic Si isotopes

TL;DR

This paper explains the shape changes in exotic silicon isotopes as a Jahn-Teller effect driven by tensor interactions, with calculations matching experimental data and predicting new features for future exploration.

Contribution

It introduces a tensor-force-driven Jahn-Teller mechanism to understand shape evolution in neutron-rich Si isotopes, supported by detailed calculations and experimental agreement.

Findings

$^{42}$Si is strongly oblate, not spherical, due to Jahn-Teller effect.

Calculations align with experimental spectroscopic factors from $^{48}$Ca(e,e'p) data.

Predicted new features for experimental investigation.

Abstract

We show how the shape evolution of the neutron-rich exotic Si and S isotopes can be understood as a Jahn-Teller effect that comes in part from the tensor-driven evolution of single-particle energies. The detailed calculations we present are in excellent agreement with known experimental data, and we point out of new features that should be explored in new experiments. Potential energy surfaces are used to understand the shape evolutions. The sub-shell closed nucleus, $^{42}$Si, is shown to be a perfect example of a strongly oblate shape instead of a sphere through a robust Jahn-Teller mechanism. The distribution of spectroscopic factors measured by $^{48}$Ca(e,e'p) experiment is shown to be well described, providing a unique test on the tensor-driven shell evolution.