Low-energy dipole excitation mode in O18 with antisymmetrized molecular dynamics

Low-energy dipole (LED) excitations in $^{18}\mathrm{O}$ were investigated using a combination of the variation after $K$ projection framework antisymmetrized molecular dynamics with $\ensuremath{\beta}$ constraint generator coordinate method. We obtained two LED states, namely, ${1}_{1}^{\ensuremath{-}}$ state dominant shell-model structure and ${1}_{2}^{\ensuremath{-}}$ large $^{14}\mathrm{C}+\ensuremath{\alpha}$ cluster component. Both these states had significant toroidal (TD) compressive (CD) strengths, indicating that TD CD modes are not separated but mixed $^{18}\mathrm{O}$. This is unlike for well-deformed nuclei such as $^{10}\mathrm{Be}$, where generated ${K}^{\ensuremath{\pi}}={0}^{\ensuremath{-}}$ ${K}^{\ensuremath{\pi}}={1}^{\ensuremath{-}}$ excitations, respectively, largely deformed state.