Effect of Parabolic Potential on Bipolaron

We apply a Feynman path-integral variational approach combining with theaverage for the relative motion to study the stability of bipolaron in aquantum dot. The binding energy is calculated in different parameters. Wefind that an optimum quantum potential favors the formation of bipolaron.Compared with other methods in literature, the present approach is betterthan Laudau-Pekar one in all coupling regime and full path-integral one inthe strong coupling regime.