Thermodynamics of pairing transition in hot nuclei

TL;DR

This paper investigates the thermodynamics of pairing transitions in hot nuclei, specifically $^{162}$Dy, using covariant density functional theory and a shell-model-like approach to analyze heat capacities and pairing correlations.

Contribution

It introduces a detailed analysis of pairing transitions in hot nuclei with exact particle number conservation, revealing the role of one-pair-broken states and a smooth pairing gap variation.

Findings

The heat capacity curve exhibits an S-shape consistent with experimental data.

One-pair-broken states are crucial for the S-shape of the heat capacity.

The pairing gap varies smoothly with temperature, indicating a gradual superfluid-normal transition.

Abstract

The pairing correlations in hot nuclei $^{162}$Dy are investigated in terms of the thermodynamical properties by covariant density functional theory. The heat capacities $C_V$ are evaluated in the canonical ensemble theory and the paring correlations are treated by a shell-model-like approach, in which the particle number is conserved exactly. A S-shaped heat capacity curve, which agrees qualitatively with the experimental data, has been obtained and analyzed in details. It is found that the one-pair-broken states play crucial roles in the appearance of the S shape of the heat capacity curve. Moreover, due to the effect of the particle-number conservation, the pairing gap varies smoothly with the temperature, which indicates a gradual transition from the superfluid to the normal state.