prof. Piotr Magierski awarded for his scientific works

The Polish Physical Society awarded prof. Piotr Magierski from our Faculty for a series of scientific papers on the dynamics of nuclear reactions, physics of quantum atomic gases, physics of neutron stars and methods of describing quantum systems of many bodies. Congratulations!

P. Magierski, B. Tüzemen, G. Wlazłowski, Spin-polarized droplets in the unitary Fermi gas, Physical Review A, 100, 033613 (2019).

We demonstrate the existence of a type of spatially localized excitations in the unitary Fermi gas: spin-polarized droplets with a peculiar internal structure involving an abrupt change in the pairing phase at the surface of the droplet. It resembles the structure of the Josephson-π junction occurring when a slice of a ferromagnet is sandwiched between two superconductors. The stability of the impurity is enhanced by the mutual interplay between the polarization effects and the pairing field, resulting in an exceptionally long-lived state. The prospects for its realization in experiments are discussed.

G. Wlazłowski, K. Sekizawa, M. Marchwiany, P. Magierski, Suppressed Solitonic Cascade in Spin-Imbalanced Superfluid Fermi Gas, Physical Review Letters, 120, 253002 (2018). 

Cold atoms experiments offer invaluable information on superfluid dynamics, including decay cascades of topological defects. While the cascade properties are well established for Bose systems, our understanding of their behavior in Fermi counterparts is very limited, in particular in spin-imbalanced systems, where superfluid (paired) and normal (unpaired) particles naturally coexist giving rise to complex spatial structure of the atomic cloud. Here we show, based on a newly developed microscopic approach, that the decay cascades of topological defects are dramatically modified by the spin-polarization. We demonstrate that decay cascades end up at different stages: "dark soliton", "vortex ring" or "vortex line", depending on the polarization. We reveal that it is caused by sucking of unpaired particles into the soliton's internal structure. As a consequence vortex reconnections are hindered and we anticipate that quantum turbulence phenomenon can be significantly affected, indicating new physics induced by polarization effects.

P. Magierski, K. Sekizawa, G. Wlazłowski, Novel Role of Superfluidity in Low-Energy Nuclear Reactions, Physical Review Letters, 119, 042501 (2017).

We demonstrate, within symmetry unrestricted time-dependent density functional theory, the existence of new effects in low-energy nuclear reactions which originate from superfluidity. The dynamics of the pairing field induces solitonic excitations in the colliding nuclear systems, leading to qualitative changes in the reaction dynamics. The solitonic excitation prevents collective energy dissipation and effectively suppresses the fusion cross section. We demonstrate how the variations of the total kinetic energy of the fragments can be traced back to the energy stored in the superfluid junction of colliding nuclei. Both contact time and scattering angle in noncentral collisions are significantly affected. The modification of the fusion cross section and possibilities for its experimental detection are discussed.

A. Bulgac, P. Magierski, K.J. Roche, I. Stetcu, Induced Fission of 240Pu within a Real-Time Microscopic Framework, Physical Review Letters, 116, 122504 (2016).

We describe the fissioning dynamics of 240Pu from a configuration in the proximity of the outer fission barrier to full scission and the formation of the fragments within an implementation of density functional theory extended to superfluid systems and real-time dynamics. The fission fragments emerge with properties similar to those determined experimentally, while the fission dynamics appears to be quite complex, with many excited shape and pairing modes. The evolution is found to be much slower than previously expected, and the ultimate role of the collective inertia is found to be negligible in this fully nonadiabatic treatment of nuclear dynamics, where all collective degrees of freedom (CDOF) are included (unlike adiabatic treatments with a small number of CDOF).

G. Wlazłowski, K. Sekizawa, P. Magierski, A. Bulgac, M. McNeil Forbes, Vortex Pinning and Dynamics in the Neutron Star Crust, Physical Review Letters, 117, 232701 (2016).

The nature of the interaction between superfluid vortices and the neutron star crust, conjectured by Anderson and Itoh in 1975 to be at the heart vortex creep and the cause of glitches, has been a long-standing question in astrophysics. Using a qualitatively new approach, we follow the dynamics as superfluid vortices move in response to the presence of “nuclei” (nuclear defects in the crust). The resulting motion is perpendicular to the force, similar to the motion of a spinning top when pushed. We show that nuclei repel vortices in the neutron star crust, and characterize the force per unit length of the vortex line as a function of the vortex element to the nucleus separation.