Optical conductivity of twisted bilayer graphene near the magic angle*

Wen, Lu; Li, Zhiqiang; He, Yan

doi:10.1088/1674-1056/abb65d

Cited by 12 publications

(11 citation statements)

References 43 publications

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“…The moiré superlattice in TBG introduces a periodic potential that can enhance the interaction between light and matter, leading to improved light absorption and carrier extraction. [155][156][157][158][159] Xin et al reported photovoltage enhancement in TBG which was achieved by adjusting the twist angle and surface plasmon resonance. The developed photodetector consisted of metal-graphene-metal lay-ers and the results show that the photovoltage intensities depend on the number of graphene layers present and the twist angle.…”

Section: Photovoltaicsmentioning

confidence: 99%

Section: Optoelectronic Applicationsmentioning

confidence: 99%

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Twisted Bilayer Graphene: A Journey Through Recent Advances and Future Perspectives

Rakkesh,

Rebecca,

Naveen

et al. 2023

Part & Part Syst Charact

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Twisted bilayer graphene (TBG) has emerged as a fascinating research frontier in condensed matter physics and materials science. This review article comprehensively overviews recent advances and future perspectives in studying TBG. The challenges associated with fabricating and characterizing TBG structures, including precise control of the twist angle and accurate determination of electronic properties, are discussed. Furthermore, the intriguing phenomena observed in TBG, such as superconductivity, insulating phases, and correlated electron states, shedding light on their underlying mechanisms, are explored. Scalability and device integration of TBG are explored, along with potential engineering strategies to tailor its properties for specific applications. By synthesizing and analyzing the latest scientific reports, a roadmap for further research is provided and the promising prospects for TBG are highlighted.

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Section: Photovoltaicsmentioning

confidence: 99%

Section: Optoelectronic Applicationsmentioning

confidence: 99%

Twisted Bilayer Graphene: A Journey Through Recent Advances and Future Perspectives

Rakkesh,

Rebecca,

Naveen

et al. 2023

Part & Part Syst Charact

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“…无论是对于TBG还是TBG-hBN体系, 平带对于这些丰富物理现象的产生都是至关重要的. 除了用转角来调控平带, 应变也是一种重要的方法, 在样品的制备过程中, 应变的产生几乎是不可避免的, 比如基底带来的应变作用: 当对两层石墨烯施加不同的应变时, 其莫尔能带将会受到调制, 原本非魔角下的TBG在此应变下也能出现平带 [9,10] ; 同时, 应变不仅能够使材料能带拓扑数发生改变 [10] , 也能够使晶格产生重构, 引发许多新奇的物理现象如孤子 [11] 、光子晶体 [12] 等; 应变相对于转角更易调控, 只需要具有压电性质的基底即可, 这使得原位调控范德瓦耳斯材料中的强关联、拓扑以及量子效应成为可能. 由此可见, 研究应变对于TBG的影响是在理论和实验上都非常有意义的.…”

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Optical conductivity of twisted bilayer graphene under heterostrain

Cai¹,

Luo²,

Li³

et al. 2021

Acta Phys. Sin.

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<sec>Twisted bilayer graphene (TBG) is a two-dimensional material composed of two layers stacked at a certain angle. When the twisted angle decreases, the lattice mismatch between two layers produces moiré pattern at a long wavelength which significantly modifies the low-energy band structure. In particular, when the twisted angle is close to the so-called “magic angle”, two moiré flat bands are formed near a charge neutral point due to the strong interlayer coupling. These flat bands with high density of states are essential in realizing superconductivity and correlated insulating states. More recently, the magic angle TBG combining an hBN system has exhibited spin-valley polarization when 3/4 of flat bands are filled, thereby providing an ideal platform to achieve quantum anomalous Hall states. Whether it is TBG system or TBG-hBN system, the flat band becomes a crucial condition for discovering so rich physical connotations. Besides the twisted angle, the strain gives an alternative way to modulate flat bands. It has been reported that applying heterostrain in magic angle TBG can makes flat moiré band tunable; strain can also generate flat bands in non-magic angle TBG. Moreover, the reconstruction of TBG due to the strain gives rise to a serial of novel physical phenomena such as topological protected soliton and photonic crystal. Another reason for studying strain effect is that the strain is ubiquitous in the fabrication progress. The strain can also be controlled via piezoelectric substrate which makes possible the in situ modulation of correlated states, topology and quantum effect. </sec><sec>Our work is to study the heterostrain effect in TBG band structure and optical conductivity by using a continuum model. Although the resulting conduction band and valence bands keep connected through Dirac points protected by the <i>C</i><sub>2</sub> symmetry, their separation increases significantly when heterostrain is applied while the Dirac point is also shifted. The optical conductivity is characterized by a series of peaks associated with van Hove singularities, and the peak energies are systematically shifted with the strain amplitude. These changes show that the heterostrain exerts a great influence on electron property of TBG.</sec>

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“…Optical experiment is a powerful technique to investigate the band structures, many body interactions and various electronic excitations in graphene-based systems [21]. The optical conductivity of TBG has been studied theoretically and experimentally in several previous works [22][23][24][25][26][27][28][29][30]. Earlier theoretical calculations [22][23][24]31] have been done for twist angles θ >= 1.47 • .…”

Section: Introductionmentioning

confidence: 99%

“…Earlier theoretical calculations [22][23][24]31] have been done for twist angles θ >= 1.47 • . More recently, the optical conductivity near the magic angle has been calculated taking into account correlation effects [25] and interlayer tunneling asymmetry [26,27]. So far, the combined effects of heterostrain and lattice * Electronic address: zhiqiangli@scu.edu.cn relaxation on the optical properties of TBG are yet to be explored.…”

Section: Introductionmentioning

confidence: 99%

Effects of heterostrain and lattice relaxation on optical conductivity of twisted bilayer graphene

Dai,

He,

2021

Preprint

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We present a theoretical study of the effects of heterostrain and lattice relaxation on the optical conductivity of twisted bilayer graphene near the magic angle, based on the band structures obtained from a continuum model. We find that heterostrain, lattice relaxation and their combination give rise to very distinctive spectroscopic features in the optical conductivity, which can be used to probe and distinguish these effects. From the spectrum at various Fermi energies, important features in the strain-and relaxation-modified band structure such as the bandgap, bandwidth and van Hove singularities can be directly measured. The peak associated with the transition between the flat bands in the optical conductivity are highly sensitive to the direction of the strain, which can provide direct information on the strain-modified flat bands.

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Optical conductivity of twisted bilayer graphene near the magic angle*

Cited by 12 publications

References 43 publications

Twisted Bilayer Graphene: A Journey Through Recent Advances and Future Perspectives

Twisted Bilayer Graphene: A Journey Through Recent Advances and Future Perspectives

Optical conductivity of twisted bilayer graphene under heterostrain

Effects of heterostrain and lattice relaxation on optical conductivity of twisted bilayer graphene

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