六角晶格中的次近邻d+id超导配对对称性

Superconducting pairing symmetry in doped honeycomb lattice

为了深入理解掺杂石墨烯中电子关联驱动的超导电性,采用约束路径量子蒙特卡罗(MC)方法,探讨了六角晶格上扩展哈伯德(Hubbard)模型中的磁和超导配对关联行为:半填充时,体系存在强的反铁磁关联,且随库仑排斥势U的增大而增大,随次近邻相互作用V的增大而减弱;偏离半填充时,低掺杂下相比其他对称性的超导配对,次近邻d+id占据主导地位,且其对较小的近邻相互作用V不敏感,但较大的V会对次近邻d+id波超导配对产生明显的抑制作用.这些结果可用于解释魔角双层石墨烯中的超导态.

To explore electron correlation-driven superconductivity in doped graphene,we use constrained path quantum Monte Carlo method to study magnetic correlation and superconducting pairing correlation in t-U-V Hubbard model on a honeycomb lattice. At half-filling this system shows strong antiferromagnetic correlation.Antiferromagnetic correlation increases with Coulomb interaction U, but is suppressed with the nearest neighbor interaction V. Away from half-filling, next-nearest-neighbor d+id pairing symmetry dominates at low doping compared to other pairing symmetries, and is insensitive to small nearest-neighbor interaction V. A larger V will,however, significantly suppress next-nearest-neighbor d+id superconducting pairing correlation. These results may lead to further understanding of superconductivity states in twisted bilayer graphene.