Moiré Phonons in Magic-Angle Twisted Bilayer Graphene

Liu, Xiaoqian; Peng, Ran; Sun, Zhaoru; Liu, Jianpeng

doi:10.1021/acs.nanolett.2c02010

Cited by 24 publications

(19 citation statements)

References 105 publications

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“…往往存在着自旋极化的向列序态, 并且垂直磁场可以诱发这类体系从自旋极化向列序态到谷极化陈绝缘体态的拓扑相变 [83,84] . 而针对转角双层石墨烯中声子性质的深度学习分子动力学研究, 发现了若干极低频率的面外"弯曲"声子模式, 并且这些极低频模式与电子耦合可能导致关联绝缘态以及电四极矩序 [85] .…”

Section: 而在各类转角多层石墨烯体系中平带在半填充时unclassified

Novel electrical properties of moiré graphene systems

Zhang¹,

Xie²,

Peng³

et al. 2023

Acta Phys. Sin.

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In this review, we discuss the electronic structures, topological properties, correlated states, nonlinear optical responses, as well as phonon and electron-phonon coupling effects of moiré graphene superlattices. First, we illustrate that topologically non-trivial flat bands and moiré orbital magnetism are ubiquitous in various twisted graphene systems. In particular, the topological flat bands of magic-angle twisted bilayer graphene (TBG) can be explained from a zeroth pseudo-Landau-level picture, which can naturally explain the experimentally observed quantum anomalous Hall effect and some of the other correlated states. These topologically nontrivial flat bands may lead to nearly quantized piezoelectric response, which can be used to directly probe the valley Chern numbers in these moiré graphene systems. A simple and general chiral decomposition rule is reviewed and discussed, which can be used to predict the low-energy band dispersions of generic twisted mulilayer graphene system and alternating twisted multilayer graphene system. This review further discusses nontrivial interaction effects of magic-angle TBG such as the correlated insulator states, density wave states, cascade transitions, and nematic states, and proposes nonlinear optical measurement as an experimental probe to distinguish the different "featureless" correlated states.The phonon properties and electron-phonon coupling effects are also briefly reviewed. The novel physics emerging from band-aligned graphene-insulator heterostructres is also discussed in this review. In the end, we make a summary and an outlook about the novel physical properties of moiré superlattices, two-dimensional materials, moiré superlattices－ two dimensional materials.

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Section: 而在各类转角多层石墨烯体系中平带在半填充时unclassified

Novel electrical properties of moiré graphene systems

Zhang¹,

Xie²,

Peng³

et al. 2023

Acta Phys. Sin.

Self Cite

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“…For that reason we take into account the role of phonons, speci cally of moiré-induced phonons also known as phasons 15 , that are still experimentally unexplored. Recent calculations demonstrate how these quasi-particles can play a crucial role in understanding the charge ordering and correlated states of magic-angle TBG 26,27 .…”

Section: Introductionmentioning

confidence: 99%

Anomalous interlayer exciton diffusion in WS2/WSe2 moiré heterostructure

Rossi

Zipfel

Maity

et al. 2023

Preprint

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Stacking van der Waals crystals allows for on-demand creation of a periodic potential landscape to tailor the transport of quasiparticle excitations. We investigate the diffusion of photoexcited electron-hole pairs or excitons at the interface of WS2/WSe2 Van der Waals heterostructure over a wide range of temperatures. We observe the appearance of distinct interlayer excitons for parallel and anti-parallel stacking, and track their diffusion through spatially and temporally resolved photoluminescence spectroscopy from 30 K to 250 K. While the measured exciton diffusivity decreases with temperature, it surprisingly plateaus below 90K. Our observations cannot be explained by classical models like hopping in the moiré potential. Using a combination of ab-initio theory and molecular dynamics simulations, we demonstrate that low energy moiré phonons, also known as phasons, play a key role in describing and understanding this anomalous behavior of exciton diffusion. In particular, we show that the moiré potential landscape is dynamic down to very low temperatures. Our observations show that the phason modes arising from the mismatched lattices of a moiré heterostructures can enable surprisingly efficient transport of energy in the form of excitons, even at low temperatures.

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“…Additionally, these methods have also been employed to study global structure optimization , and the reaction mechanisms . Among these NN-based methods, DPMD is extensively used in different materials systems for its ab initio accuracy and high efficiency. − …”

Section: Introductionmentioning

confidence: 99%

High-Accuracy Machine-Learned Interatomic Potentials for the Phase Change Material Ge₃Sb₆Te₅

Zhang

Wan

et al. 2023

Chem. Mater.

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Ge3Sb6Te5 with an emerging off-stoichiometric composition has been proven to have characteristic properties of phase change materials (PCMs) by experiments. However, the detailed mechanism of the phase transition and the highly temperature-dependent kinetics of its crystallization process have yet to be resolved at the atomic scale. In this work, we develop an artificial neural network-based potential (NNP) to accelerate the molecular dynamics (MD) simulation of Ge3Sb6Te5 without sacrificing the quantum mechanical accuracy. Overall, the comprehensive structural information predicted by NNP shows an excellent agreement with that of ab initio MD (AIMD), indicating the reliability of the proposed method. Based on the well-trained NNP, an MD simulation can be adopted to simulate Ge3Sb6Te5 with over 10,000 atoms with high efficiency and accuracy, which is beyond the reach of AIMD. Subsequently, a further NNP-based MD simulation with long timescales is carried out, which successfully captures the rapid transition of the crystallization and perfectly reproduces the crystallization process consistent with experiments. This work provides a novel atomic-level simulation and analysis approach to the complex Ge3Sb6Te5 and makes it possible to simulate the real nonvolatile memory device.

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Moiré Phonons in Magic-Angle Twisted Bilayer Graphene

Cited by 24 publications

References 105 publications

Novel electrical properties of moiré graphene systems

Novel electrical properties of moiré graphene systems

Anomalous interlayer exciton diffusion in WS2/WSe2 moiré heterostructure

High-Accuracy Machine-Learned Interatomic Potentials for the Phase Change Material Ge₃Sb₆Te₅

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Moiré Phonons in Magic-Angle Twisted Bilayer Graphene

Cited by 24 publications

References 105 publications

Novel electrical properties of moiré graphene systems

Novel electrical properties of moiré graphene systems

Anomalous interlayer exciton diffusion in WS2/WSe2 moiré heterostructure

High-Accuracy Machine-Learned Interatomic Potentials for the Phase Change Material Ge3Sb6Te5

Contact Info

Product

Resources

About

High-Accuracy Machine-Learned Interatomic Potentials for the Phase Change Material Ge₃Sb₆Te₅