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arXiv · 2411.19052

Phase diagrams of neutron-proton superfluid in asymmetric nuclear matter

K. D. Duan·H. B. Zhang·X. L. Shang
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Abstract

The finite-temperature phase structures for neutron-proton superfluidity in asymmetric nuclear matter are investigated, with a particular focus on the angular dependence of the pairing gap induced by the $^3SD_1$ $NN$ interaction. This angular dependence of the pairing gap results in the Cooper pair momentum in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state exhibiting exactly two distinct stable orientations: one orthogonal (FFLO-ADG-O) and the other parallel (FFLO-ADG-P) to the symmetry axis of the pairing gap. The FFLO-ADG-O state dominates at low asymmetries, while the FFLO-ADG-P state prevails at high asymmetries. Additionally, these analysis of normal-superfluid phase separation reveals that the angular dependence of the pairing gap eliminates phase separation in the low-asymmetry regime, whereas the Cooper pair momentum effectively suppresses phase separation at high asymmetries. These two mechanisms act in concert to significantly prevent the occurrence of normal-superfluid phase separation across the entire phase diagram, ensuring the stability of the homogeneous superfluid state over a broad range of asymmetries. These results provide new insights into the interplay between the angular dependence of the pairing gap and the stability of superfluidity in asymmetric nuclear matter.

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K. D. Duan, H. B. Zhang, X. L. Shang. 2024-11-28. Phase diagrams of neutron-proton superfluid in asymmetric nuclear matter. https://doi.org/10.1103/physrevc.111.014320

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