Twistronics: a turning point in 2D quantum materials

Abstract

Moiré superlattices—periodic orbital overlaps and lattice-reconstruction between sites of high atomic registry in vertically-stacked 2D layered materials—are quantum-active interfaces where non-trivial quantum phases on novel phenomena can emerge from geometric arrangements of 2D materials, which are not intrinsic to the parent materials. Unexpected distortions in band-structure and topology lead to long-range correlations, charge-ordering, and several other fascinating quantum phenomena hidden within the physical space between the (similar or dissimilar) parent materials. Stacking, twisting, gate-modulating, and optically-exciting these superlattices open up a new field for seamlessly exploring physics from the weak to strong correlations limit within a many-body and topological framework. It is impossible to capture it all, and the aim of this review is to highlight some of the important recent developments in synthesis, experiments, and potential applications of these materials.

Evidence for highly p-type doping and type II band alignment in large scale monolayer WSe2/Se-terminated GaAs heterojunction grown by molecular beam epitaxy

“…34 In hybrid van der Waals heterostructures, made of 2D/3D van der Waals materials, the strain in the 2D TMD layer can be engineered by changing the relative crystallographic orientation between the WSe 2 and the GaAs substrate, notably the angular misorientation, also known as the "twist angle". 35,36 In this work, we report high p-type doping stabilized in the monolayer WSe 2 via an electron transfer from the WSe 2 to the Se-terminated GaAs substrate. A large area single layer WSe 2 film was grown by molecular beam epitaxy (MBE) on a Se-terminated GaAs(111)B substrate.…”

The optical response of artificially twisted MoS$$_2$$ bilayers

“…The simplistic approach of producing vertical vdW heterostructures without the constraints of crystal lattice mismatch enables integrating various 2D materials to create diverse systems with new electronic properties that are not present in pristine components. In addition to the selection of compounds in terms of their properties, a new degree of freedom has emerged: the twist angle between stacked layers, which gives rise to the group of the so-called twistronic materials 14 , 15 . The twist angle is responsible for the occurrence of moiré patterns, that leads to new and intriguing phenomena, like the formation of secondary Dirac points in graphene on hexagonal boron nitride (hBN) 16 , 17 or hybridized (moiré) excitons in vdW heterostructures formed by stacked two S-TMD MLs 18 – 23 .…”

Proximity spin-orbit and exchange coupling in ABA and ABC trilayer graphene van der Waals heterostructures

“…In twisted vdW heterostructures [42][43][44][45] the interlayer interaction can be controlled by the twist angle. In this context, bilayer graphene (BLG) was the first model playground for gate-and twist-tunable correlated physics [44,[46][47][48][49][50][51], as well as for layer-dependent proximityinduced spin interactions [12,[52][53][54][55][56][57][58][59][60].…”