Phys. Rev. Lett. (in the press); preprint at https://arxiv.org/abs/1606.09056

Electron dynamics usually steal the show when we talk about atoms. But that doesn't mean that atomic nuclei are simply static. The collective motion of nucleons is what creates a particular nuclear shape and understanding how this works can help us to manipulate exotic nuclei. So what about isotopes? Their nuclei always host the same number of protons, but when we start adding neutrons, things can get pretty crowded — leading to nuclear shape deformation.

Typically, increasing the number of neutrons leads to a gradual change in the nuclear shape, for instance from spherical to prolate or oblate. But Tomoaki Togashi and colleagues have now established that this is not the case for zirconium, whose nuclear shape undergoes an abrupt deformation at around 60 neutrons. By performing systematic large-scale Monte Carlo shell-model calculations, the authors were able to reproduce this sudden nuclear reorganization — and demonstrate that it behaves as a quantum phase transition.