Tetrahedral shape and Lambda impurity effect in⁸⁰Zr with a multidimensionally constrained relativistic Hartree-Bogoliubov model

Abstract：

This study investigated the tetrahedral structure in ⁸⁰Zr and Lambda (Λ) impurity effect in $ ^{81}_{\; \Lambda} $ Zr using the multidimensionally constrained relativistic Hartree-Bogoliubov model. The ground states of both ⁸⁰Zr and $ ^{81}_{\; \Lambda} $ Zr exhibit a tetrahedral configuration, accompanied by prolate and axial-octupole shaped isomers. Our calculations reveal that there are changes in the deformation parameters $ \beta_{20} $ , $ \beta_{30} $ , and $ \beta_{32} $ upon Λ binding to ⁸⁰Zr, except for $ \beta_{32} $ when Λ occupies p-orbits. Compared to the two shape isomers, the Λ particle exhibits weaker binding energy in the tetrahedral state when occupying the $ 1/2^+[000](\Lambda_s) $ or $ 1/2^-[110] $ single-particle state. In contrast, the strongest binding occurs for the Λ particle in the $ 1/2^-[101] $ state with tetrahedral shape. Besides, a large Λ separation energy may not necessarily correlate with a significant overlap between the density distributions of the Λ particle and nuclear core, particularly for tetrahedral hypernuclei.