Graphene rolls with tunable chirality

Abstract

Creating chirality in achiral graphene and other two-dimensional materials has attracted broad scientific interest due to their potential application in advanced optics, electronics and spintronics. However, investigations into their optical activities and related chiro-electronic properties are constrained by experimental challenges, particularly in the precise control over the chirality of these materials. Here a universal wax-aided immersion method is developed to yield graphene rolls with controllable chiral angles, and the method can be generalized in other two-dimensional materials for high-yield fabrication. The left-handed and right-handed rolls exhibit optical activity and excellent spin selectivity effects with a spin polarization over 90% at room temperature. The discovery of tunable chirality-induced spin selectivity in tailored roll-shaped allotropes, achievable only through precise control of chirality, distinguishes itself from other carbon materials or existing chiral materials. Our Dirac fermion model shows that the electrons moving predominately along one side of the chiral roll develop a preferred spin polarization, and the rolling-chirality-induced spin selectivity is a result of this finite spin selectivity effect. Our method opens up opportunities for endowing achiral two-dimensional materials with tunable chirality, and may enable the emergence of quantum behaviours and room-temperature spintronic technologies.