Nuclear pairing at finite temperature and angular momentum

TL;DR

This paper introduces a new theoretical approach to nuclear pairing at finite temperature and angular momentum, accounting for quasiparticle fluctuations and pair vibrations, leading to more accurate predictions of pairing gaps and phase transitions.

Contribution

It develops a self-consistent quasiparticle random-phase approximation method that improves understanding of nuclear pairing behavior at finite temperature and angular momentum.

Findings

Thermal pairing gap persists beyond the BCS critical temperature.

Sharp phase transition is smoothed out at moderate and strong couplings.

Thermally assisted pairing appears in hot rotating nuclei.

Abstract

An approach is proposed to nuclear pairing at finite temperature and angular momentum, which includes the effects of the quasiparticle-number fluctuation and dynamic coupling to pair vibrations within the self-consistent quasiparticle random-phase approximation. The numerical calculations of pairing gaps, total energies, and heat capacities are carried out within a doubly folded multilevel model as well as several realistic nuclei. The results obtained show that, in the region of moderate and strong couplings, the sharp transition between the superconducting and normal phases is smoothed out, causing a thermal pairing gap, which does not collapse at a critical temperature predicted by the conventional Bardeen-Cooper-Schrieffer's (BCS) theory, but has a tail extended to high temperatures. The theory also predicts the appearance of a thermally assisted pairing in hot rotating nuclei.