The evolution of spin-orbit splittings of neutron drops along with the neutron number and its connection with the tensor-force strength have been investigated systematically for different external fields in the relativistic Brueckner-Hartree-Fock (RBHF) and relativistic Hartree-Fock (RHF) theories. Based on the RHF functional PKO1, it is found that a good consistency between the RBHF and RHF results for the total energies can be obtained only for those neutron drops whose central densities are close to the saturation density of nuclear matter. Nevertheless, by rescaling the density dependence of the RHF functional, the RBHF total energies of neutron drops in different external fields can be well reproduced. The optimized tensor-force strength $\lambda$ in the RHF theory, which reproduces the microscopic RBHF spin-orbit splittings, is running with the strength of the external fields of neutron drops. This provides an important guide for future determination of tensor forces in nuclear energy density functionals based on microscopic ab initio calculations.

• Received 8 August 2019
• Revised 18 October 2019

DOI:https://doi.org/10.1103/PhysRevC.100.064319