Effects of mean-field and pairing correlations on the Bogoliubov quasiparticle resonance

• Published in: Science China. Physics, mechanics & astronomy Vol. 62; no. 11; p. 112012
• Main Authors: Qu, XiaoYing, Zhang, Ying
• Format: Journal Article
• Language: English
• Published: Beijing Science China Press 01.11.2019; Springer; Springer Nature B.V
• Subjects: Angular momentum; Approximation; Astronomy; Bogoliubov theory; Boundary conditions; Classical and Continuum Physics; Correlation; Density; Electrons; Elementary excitations; Energy; Green's functions; Hartree approximation; Investigations; Observations and Techniques; Physics; Physics and Astronomy; Spectra; quasiparticle resonance; pairing correlations; Skyrme Hartree-Fock-Bogoliubov theory; Green’s function method; mean-field
• ISSN: 1674-7348; 1869-1927
• DOI: 10.1007/s11433-019-9409-y

The quasiparticle resonances are investigated by examining three kinds of quasiparticle spectra, i.e., the density of quasiparticle states, the occupation number density, and the pair number density in the continuum Skyrme Hartree-Fock-Bogoliubov theory with the Green’s function method. Taking the weakly bound nucleus 66 Ca as an example, the quasiparticle resonant energies and widths extracted from these three kinds of quasiparticle spectra are compared. For the narrow resonances, the extracted resonant energy and the width are consistent with each other. However, it is difficult to use the density of quasiparticle states to identify the broad resonances due to the background of nonresonant continuum. By switching off the pairing potential and/or the Hartree-Fock (HF) potential respectively in the calculation of these quasiparticle spectra, the roles of HF mean-field and pairing correlations in the quasiparticle resonances are demonstrated clearly. It turns out that all the quasiparticle resonances corresponding to the deeply bound, weakly bound and positive-energy single-particle resonant states, are mainly contributed by the HF potential. The pairing potential helps to slightly increase the resonant energy and the width. However, the pairing potential is important to make the nucleons occupy the low-lying nonresonant continuum states near the threshold and take part in the pairing correlations here, especially for the partial waves with small angular momentum ℓ.