Origin of the drastic decrease of fusion probability in superheavy mass region

The fusion-fission process in the superheavy mass region is studied systematically by solving the time evolution of nuclear shape in three-dimensional deformation space using the Langevin equation. By analyzing the trajectory in the deformation space, we identify the critical area when the trajectory's destination is determined to be the fusion or the quasi-fission process. It is also clarified that the potential landscape around the critical area is crucial for estimating the fusion probability, and its dependence on the atomic number is presented.