Relativistic stability of positronium atoms in a linearly polarized high frequency super-intense laser field

Utilizing the relativistically corrected Krammers-Henneberger (KH) potential in the high frequency Floquet theory (HFFT), the ground state of the positronium (Ps) atom in a linearly polarized high frequency super-intense laser field is investigated numerically. It is reported that the relativistic effect can prevent Ps from annihilating into γ rays, thus enhancing its stability. The underlying mechanism lies in the reconstruction of the electron wavefunction into a figure-of-eight shape, which leads to an effective reduction of the electron-positron overlapping probability.