Electrically controlled superconducting states at the heterointerface SrTiO₃/LaAlO₃

We study the symmetry of Cooper pair in a two-dimensional Hubbard model with the Rashba-type spin-orbit interaction as a minimal model of electron gas generated at a heterointerface of SrTiO₃/LaAlO₃. Solving the Iliashberg equation based on the third-order perturbation theory, we find that the gap function consists of the mixing of the spin-singlet d_xy -wave component and the spin-triplet (p_x ±ip_y) -wave one due to the broken inversion symmetry originating from the Rashba-type spin-orbit interaction. The ratio of the d -wave and the p -wave component continuously changes with the carrier concentration. We propose that the pairing symmetry is controlled by tuning the gate voltage.