▎ 摘　　要

Strong circular dichroism (CD) effect has gained great interest in nano-optical sensing and detection due to its desirable applications. In this work, we theoretically demonstrate that CD effects can be extremely enhanced in hybrid graphene-metal metamaterials at the near-infrared region. Benefiting from the strong coupling between graphene sheets and chiral metal nanocrystals, the maximum peak value of CD responses can be reached at 9.2% and the other peak value is more than twice as much as the without-graphene systems. When there is one more graphene layer covered on the chiral nanocrystals, the CD responses increase further. For single-layer graphene nanoribbons covered on the spacer, the CD response increases with the increasing filling ratio. The simulation results show that the CD response decreases rapidly with the increase of the distance between the chiral nanocrystals and the graphene sheet. Besides, with the increase of the thickness of the spacer, two CD resonance peaks, one increases faster and the other goes from decreasing to increasing compared with the without-graphene systems. Overall, we can greatly enhance CD effects in the near-infrared region by adding graphene layers, which can provide potential applications in the fields of biosensing and optoelectronic devices.