Tunable Optical Activity in Twisted Anisotropic Two-Dimensional Materials

Abstract

Twisted van der Waals structures exhibit a variety of unusual electrical and optical phenomena and could provide a powerful means for designing nanodevices with tunable chiral properties. However, programming intrinsic chiral properties of the film on the atomic scale remains a great challenge due to the limitations of fabrication and measurement techniques. Here, we report a highly tunable large optical activity of twisted anisotropic two-dimensional (2D) materials, including black phosphorus (BP), ReS 2 , PdSe 2 , and α-MoO 3 , by varying the twist angle between the stacked layers. The chirality can be deliberately tailored through the engineering of the symmetry, band structure, and anisotropy of 2D materials, demonstrating the high tunability of the chirality. The results show the highest thickness-normalized ellipticity value (13.8 deg μm −1 , twisted ReS 2 ) and ellipticity value (1581 mdeg, twisted BP) among the systems based on 2D materials. It is also shown that the chiroptical response exists in an extremely large spectral range from the visible to the infrared. Furthermore, the twisted ReS 2 enabled spin-selective control of the information transformation. These results show that highly controllable chirality in twisted 2D anisotropic materials has considerable potential in on-chip polarization optics, nano-optoelectronics, and biology.

Observation of Chirality Transfer in Twisted Few-Layer Graphene

“…Twisted graphene structures are schematically demonstrated in Figure a, where achiral few-layer graphene components with varied layers are stacked with an interlayer twist to create a helical structure. The helicity breaks the three-dimensional symmetry of the graphene superlattice, hence producing structural chirality. , For simplicity of reference, samples are named t­( m + n )­LG, where m refers to the layer number of the top layer and n refers to the layer number of the bottom layer. Where handedness is specified, the prefix “RH” is designated to right-handed samples, which are defined as structures with the top layer rotated clockwise relative to the bottom layer.…”

“…Controllable chirality can be realized through interlayer twist of atomically thin films, such as graphene and boron nitride. − The circular dichroism (CD) of twisted bilayer graphene on a centimeter scale was experimentally observed and attributed to the electromagnetic coupling that is facilitated by optically induced interlayer electronic transitions . Recently, twist engineering with ReS 2 and black phosphorus further demonstrated the ubiquity of twist-controlled chiroptical response . Raman optical activity (ROA), which characterizes chiroptical response by measuring the Raman scattering intensity difference of chiral species probed with right-circularly polarized (RCP) and left-circularly polarized (LCP) light, has been observed in 2D materials such as ReS 2 and TaS 2 , , which originates from the planar chirality intrinsic to the lattice of ReS 2 and TaS 2 .…”

Degree of disorder-regulated ion transport through amorphous monolayer carbon

“…Our results introduce a DOD-tuned membrane material, holding immense potential for novel nanodevices and filtration technologies through strategic nanopore manipulations, unlocking 2D amorphous materials' applications in mass separation, energy storage, and sensing. 30…”

“…If so, this could pave the way for a novel membrane material that retains nature-made channels for ion transmembrane transport, while still maintaining its ultrathin properties. 30,31 Fortunately, very recently, 2DAMs have been experimentally synthesized, such as carbon, boron nitride, and transition metal dichalcogenides. 32–35 Novel properties stemming from their structures, such as an ultra-low dielectric constant and superior catalytic performance, have been revealed.…”