Superfluid transition temperature of bond bipolarons with Coulomb interaction

Abstract: Utilizing an exactly sign-problem-free quantum Monte Carlo method, we explore the influence of long-range Coulomb interaction on the superfluid transition temperature of bipolarons in a two dimensional square lattice. The model studied here is the bond Su-Schrieffer-Heeger model with phonon-modulated electron hopping. Previously, in the absence of long-range Coulomb interaction, this model demonstrated the emergence of small-size, light-mass bipolarons that undergo a superfluid transition at high values of the transition temperature $T_c$ [Physical Review X 13, 011010, (2023)]. Our findings indicate that with the long-range Coulomb interaction, $T_c$ remains relatively high, even in the deep adiabatic regime where the phonon frequency $\omega/t = 0.5$ and the Coulomb interaction $V = U/10$. This result suggests a relatively high superfluid transition temperature for bond bipolarons with long range Coulomb interaction in the low-density regime, which could provide a new insights for the future experiments on dilute superconductors.