Best poster award for PhD student

We present results of collisions of medium mass nuclei, 90Zr+90Zr and 96Zr+96Zr obtained within time-dependent density functional theory (TDDFT) extended to superfluid systems, known as 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 [1], 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 U(1) symmetry breaking, which leads to large-amplitude oscillations of pairing field and bear similarity to the pairing Higgs mechanism.

Pairing correlations in nuclear systems are one of the best known characteristics of non-magic atomic nuclei [2-4]. Various features related to high spin phenomena, indicate that these correlations are crucial for our understanding of nuclear structure and dynamics. Pairing in atomic nuclei is usually theoretically described on a mean-field level, where the concept of pairing field plays the key role. It implicitly assumes the existence of superfluid phase described by the complex field playing the role of the order parameter. Although the average magnitude of this field is an important ingredient of any theoretical description of medium or heavy nuclei, the other features related to this degree of freedom are usually omitted in the context of nuclear dynamics. These features include spatial modulations (oscillations) of the order parameter, where both the magnitude and the phase may vary in space and time.

References
[1] P. Magierski et al., Phys. Rev. Lett. 119, 042501 (2017)
[2] P. Ring and P. Schuck, Springer Science Business Media (2004)
[3] D.J. Dean and M. Hjorth-Jensen, Rev. Mod. Phys. 75, 607 (2003).
[4] D.M. Brink and R.A. Broglia, Cambridge University Press (2005).

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