Pairing dynamics and solitonic excitations in collisions of medium-mass, identical nuclei

Abstract

We present results of collisions of $^{90}\mathrm{Zr}+^{90}\mathrm{Zr}$ and $^{96}\mathrm{Zr}+^{96}\mathrm{Zr}$ obtained within time-dependent density functional theory (TDDFT) extended to superfluid systems, known as the time-dependent superfluid local density approximation (TDSLDA). We discuss qualitatively new features occurring in collisions of two superfluid nuclei at energies in the vicinity of the Coulomb barrier. We show that a solitonic excitation---an abrupt pairing phase distortion---reported previously [P. Magierski et al., Phys. Rev. Lett. 119, 042501 (2017)] increases the barrier for capture, generating effective repulsion between colliding nuclei. Moreover we demonstrate that pairing field leads to qualitatively different dynamics at the Coulomb barrier which manifests itself in a slower evolution of deformation towards a compact shape. Last but not least, we show that magnitude of pairing correlations can be dynamically enhanced after collision. We interpret it as a dynamically induced $\text{U}(1)$ symmetry breaking, which leads to large-amplitude oscillations of pairing field and bears similarity to the pairing Higgs mechanism.