Nature of the effective interaction in electron-doped cuprate superconductors: A sign-problem-free quantum Monte Carlo study

Understanding the mechanism of Cooper pairing amounts to determining the effective interaction that operates at low energies. Efforts to achieve such a goal for superconducting materials, especially strongly correlated ones, from both bottom-up and top-down approaches, have been plagued by having to use uncontrolled approximations. Here, we perform large-scale, numerically exact, sign-problem-free zero-temperature quantum Monte Carlo simulations on an effective theory based on "hot spots" plus fluctuating collective modes. Because hot spots are clearly identified by angle-resolved photoemission spectroscopy for electron-doped cuprates, we focus our attention on such materials. Our goal is to determine the minimum effective action that can describe the observed superconductivity and charge-density wave. The results suggest that antiferromagnetic fluctuation alone is not sufficient-the effective action needs to be amended with nematic fluctuations. We believe that our results address the pairing mechanism of high-T-c superconductivity in electron-doped cuprates, and they shed light on the pairing mechanism of hole-doped cuprates.