We extend the relativistic Hartree-Fock (RHF) theory to study the structure of single-$Λ$ hypernuclei. The density dependence is taken in both meson-nucleon and meson-hyperon coupling strengths, and the induced $Λ$-nucleon ($ΛN$) effective interactions are determined by fitting $Λ$ separation energies to the experimental data for several single-$Λ$ hypernuclei. The equilibrium of nuclear dynamics described by the RHF model in normal atomic nuclei, namely, the balance between nuclear attractive and repulsive interactions, is then found to be drastically changed in single-$Λ$ hypernuclei, revealing a different role of Fock terms via $Λ$ hyperon from the nucleon exchange. Since only one hyperon exists in a single-$Λ$ hypernucleus, the overwhelmed $ΛN$ and $ΛΛ$ attractions via the Hartree than the $ΛΛ$ repulsion from the Fock terms require an alternation of meson-hyperon coupling strengths in RHF to rebalance the effective nuclear force with the strangeness degree of freedom, leading to an improved description of $Λ$ Dirac mass and correspondingly a systematically reduced $σ$-$Λ$ coupling strength $g_{σΛ}$ in current models as compared to those relativistic mean-field (RMF) approaches without Fock terms. As a result, the effective $Λ$ spin-orbit coupling potential in the ground state of hypernuclei is suppressed, and these RHF models predict correspondingly a quenching effect in $Λ$ spin-orbit splitting in comparison with the RMF cases. Furthermore, the $Λ$ spin-orbit splitting could decrease efficiently by evolving the hyperon-relevant couplings $g_{σΛ}$ and $g_{ωΛ}$ simultaneously, where to reconcile with the empirical value the RHF models address a larger parameter space of meson-hyperon couplings.
Quadrupole deformation $(β,γ)$ of light $Λ$ hypernuclei in constrained relativistic mean field model: shape evolution and shape polarization effect of $Λ$ hyperon
Microscopic Calculation of Electric Quadrupole Effective Charges in Exotic Nuclei
University of South China（南华大学）；Key Laboratory of Advanced Nuclear Energy Design and Safety, Ministry of Education（教育部先进核能设计与安全重点实验室）；Guizhou Minzu University（贵州民族大学）；Shanghai Jiao Tong University（上海交通大学）；Shanghai Key Laboratory for Particle Physics and Cosmology（上海粒子物理与宇宙学重点实验室）；Lanzhou University（兰州大学）；Key Laboratory of Special Function Materials and Structure Design（特殊功能材料与结构设计重点实验室）
