Electric field-induced chiral d + id superconductivity in AA-stacked bilayer graphene: a quantum Monte Carlo study.

Using the constrained-path quantum Monte Carlo method, we systematically study the half-filled Hubbard model on AA-stacked honeycomb lattice. Our simulations demonstrate that a dominant chiral d + id wave superconductivity can be induced by a perpendicular electric field. At a fixed electric field, the effective pairing interaction of chiral d + id superconductivity exhibits an increasing behavior with increasing the on-site Coulomb interaction. We attribute the electric field-induced d + id superconductivity to an increased density of states near the Fermi energy and robust antiferromagnetic spin correlation upon turning on electric field. Our results strongly suggest that the AA-stacked graphene system is a good candidate for chiral d + id superconductor.

Possible cluster pairing correlation in the checkerboard Hubbard model: a quantum Monte Carlo study.

Constrained-path quantum Monte Carlo method is applied to study the pairing correlation in the checkerboard Hubbard model with inhomogeneous nearest-neighbor hopping at a low doping of holes. The inhomogeneous hopping can enhance the pairing correlation among different plaquette clusters. An obvious maximum for the pairing correlation is observed at a certain inhomogeneous hopping. The cluster pairing correlation shows the strongest long-range behavior at the optimal inhomogeneity. The enhancement of cluster pairing correlation might be associated with the transition of the Fermi surface structure. This work indicates that the inhomogeneous hopping could tailor the pairing correlation effectively.

Interplay between nematic fluctuation and superconductivity in a two-orbital Hubbard model: a quantum Monte Carlo study.

To understand the interplay between nematic fluctuation and superconductivity in iron-based superconductors, we performed a systematic study of the realistic two-orbital Hubbard model at intermedium correlation regimes by using the constrained-path quantum Monte Carlo method. Our numerical results showed that the on-site nematic interaction induces a strong enhancement of nematic fluctuations at various momentums, especially at ([Formula: see text]). Simultaneously, it was found that the on-site nematic interaction suppresses the [Formula: see text] antiferromagnetic order and long-range electron pairing correlations for dominant pairing channels. Our findings suggest that on-site nematic fluctuation seems to compete with superconductivity in iron-based superconductors.