Correlated states in doubly-aligned hBN/graphene/hBN heterostructures

AbstractInterfacial moiré superlattices in van der Waals vertical assemblies effectively reconstruct the crystal symmetry, leading to opportunities for investigating exotic quantum states. Notably, a two-dimensional nanosheet has top and bottom open surfaces, allowing the specific case of doubly aligned super-moiré lattice to serve as a toy model for studying the tunable lattice symmetry and the complexity of related electronic structures. Here, we show that by doubly aligning a graphene monolayer to both top and bottom encapsulating hexagonal boron nitride (h-BN), multiple conductivity minima are observed away from the main Dirac point, which are sensitively tunable with respect to the small twist angles. Moreover, our experimental evidences together with theoretical calculations suggest correlated insulating states at integer fillings of −5, −6, −7 electrons per moiré unit cell, possibly due to inter-valley coherence. Our results provide a way to construct intriguing correlations in 2D electronic systems in the weak interaction regime.

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Towards Understanding the Raman Spectrum of Graphene Oxide: The Effect of the Chemical Composition

Coatings ◽

10.3390/coatings10060524 ◽

2020 ◽

Vol 10 (6) ◽

pp. 524 ◽

Cited By ~ 1

Author(s):

David López-Díaz ◽

Juan A. Delgado-Notario ◽

Vito Clericò ◽

Enrique Diez ◽

María Dolores Merchán ◽

...

Keyword(s):

Graphene Oxide ◽

Raman Spectrum ◽

Chemical Composition ◽

Hexagonal Boron Nitride ◽

Theoretical Calculations ◽

Periodic Lattice ◽

Graphene Monolayer ◽

Atomic Configuration ◽

Different Types ◽

Defects In Semiconductors

Raman spectroscopy is a technique widely used to detect defects in semiconductors because it provides information of structural or chemical defects produced in its structure. In the case of graphene monolayer, the Raman spectrum presents two bands centered at 1582 cm−1 (G band) and 2700 cm−1 (2D band). However, when the periodic lattice of graphene is broken by different types of defects, new bands appear. This is the situation for the Raman spectrum of graphene oxide. It is well established that the existence of these bands, the position and the intensity or width of peaks can provide information about the origin of defects. However, in the case of the graphene oxide spectrum, we can find in the literature several discrepant results, probably due to differences in chemical composition and the type of defects of the graphene oxide used in these studies. Besides, theoretical calculations proved that the shape of bands, intensity and width, and the position of graphene oxide Raman spectrum depend on the atomic configuration. In the current work, we will summarize our current understanding of the effect of the chemical composition on the Raman spectrum of graphene oxide. Finally, we apply all this information to analyze the evolution of the structure of graphene oxide during the thermal annealing of the heterostructures formed by graphene oxide sandwiches in a hexagonal boron nitride.

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Magnetoexcitons in two-dimensional electronic systems

Uspekhi Fizicheskih Nauk ◽

10.3367/ufnr.0185.201504a.0337 ◽

2015 ◽

Vol 185 (4) ◽

pp. 337-352

Author(s):

Veronika E. Bisti ◽

Aleksandr B. Van'kov ◽

Andrei S. Zhuravlev ◽

Leonid V. Kulik

Keyword(s):

Electronic Systems ◽

Two Dimensional

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Pyrrole-bridged quinones: π-electronic systems that modulate electronic structures by tautomerism and deprotonation

Chemical Communications ◽

10.1039/d1cc02691g ◽

2021 ◽

Author(s):

Shinya Sugiura ◽

Hiromitsu Maeda

Keyword(s):

Infrared Absorption ◽

Electronic Structures ◽

Near Infrared ◽

Ion Pairing ◽

Anion Binding ◽

Electronic Systems

A new series of π-extended quinone derivatives containing a pyrrole bridge exhibited NH/OH-type tautomerization and anion binding along with deprotonation that induced near-infrared absorption and ion-pairing assemblies.

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Electronic structures of iMAX phases and their two-dimensional derivatives: A family of piezoelectric materials

Physical Review Materials ◽

10.1103/physrevmaterials.2.074002 ◽

2018 ◽

Vol 2 (7) ◽

Cited By ~ 11

Author(s):

Mohammad Khazaei ◽

Vei Wang ◽

Cem Sevik ◽

Ahmad Ranjbar ◽

Masao Arai ◽

...

Keyword(s):

Electronic Structures ◽

Piezoelectric Materials ◽

Two Dimensional

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Emergent flat band electronic structure in a VSe2/Bi2Se3 heterostructure

Communications Materials ◽

10.1038/s43246-020-00115-w ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Turgut Yilmaz ◽

Xiao Tong ◽

Zhongwei Dai ◽

Jerzy T. Sadowski ◽

Eike F. Schwier ◽

...

Keyword(s):

Dirac Point ◽

Electronic States ◽

Quantum States ◽

Photoemission Spectroscopy ◽

Flat Band ◽

Strongly Correlated ◽

Dirac Cone ◽

Angle Resolved Photoemission Spectroscopy ◽

Topological Materials ◽

Photoemission Study

AbstractFlat band electronic states are proposed to be a fundamental tool to achieve various quantum states of matter at higher temperatures due to the enhanced electronic correlations. However, materials with such peculiar electronic states are rare and often rely on subtle properties of the band structures. Here, by using angle-resolved photoemission spectroscopy, we show the emergent flat band in a VSe2 / Bi2Se3 heterostructure. Our photoemission study demonstrates that the flat band covers the entire Brillouin zone and exhibits 2D nature with a complex circular dichroism. In addition, the Dirac cone of Bi2Se3 is not reshaped by the flat band even though they overlap in proximity of the Dirac point. These features make this flat band distinguishable from the ones previously found. Thereby, the observation of a flat band in the VSe2 / Bi2Se3 heterostructure opens a promising pathway to realize strongly correlated quantum effects in topological materials.

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A comparison of different approaches to enforce lattice symmetry in two‐dimensional crystals

PAMM ◽

10.1002/pamm.202000192 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Rainer Backofen ◽

Lisa Sahlmann ◽

Anna Willmann ◽

Axel Voigt

Keyword(s):

Two Dimensional ◽

Lattice Symmetry

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Water friction in nanofluidic channels made from two-dimensional crystals

Nature Communications ◽

10.1038/s41467-021-23325-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Ashok Keerthi ◽

Solleti Goutham ◽

Yi You ◽

Pawin Iamprasertkun ◽

Robert A. W. Dryfe ◽

...

Keyword(s):

Hexagonal Boron Nitride ◽

Slip Length ◽

Two Dimensional ◽

Water Flows ◽

Nanofluidic Channels ◽

Molecular Separation ◽

Solid Liquid Interface ◽

Solid Liquid ◽

Biological Channels ◽

Atomically Flat

AbstractMembrane-based applications such as osmotic power generation, desalination and molecular separation would benefit from decreasing water friction in nanoscale channels. However, mechanisms that allow fast water flows are not fully understood yet. Here we report angstrom-scale capillaries made from atomically flat crystals and study the effect of confining walls’ material on water friction. A massive difference is observed between channels made from isostructural graphite and hexagonal boron nitride, which is attributed to different electrostatic and chemical interactions at the solid-liquid interface. Using precision microgravimetry and ion streaming measurements, we evaluate the slip length, a measure of water friction, and investigate its possible links with electrical conductivity, wettability, surface charge and polarity of the confining walls. We also show that water friction can be controlled using hybrid capillaries with different slip lengths at opposing walls. The reported advances extend nanofluidics’ toolkit for designing smart membranes and mimicking manifold machinery of biological channels.

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A Universal Atomic Substitution Conversion Strategy Towards Synthesis of Large-Size Ultrathin Nonlayered Two-Dimensional Materials

Nano-Micro Letters ◽

10.1007/s40820-021-00692-6 ◽

2021 ◽

Vol 13 (1) ◽

Author(s):

Mei Zhao ◽

Sijie Yang ◽

Kenan Zhang ◽

Lijie Zhang ◽

Ping Chen ◽

...

Keyword(s):

Theoretical Calculations ◽

2D Materials ◽

Direct Synthesis ◽

Two Dimensional ◽

Covalent Bonds ◽

2D Layered Materials ◽

Large Size ◽

Two Dimensional Materials ◽

Microfabrication Technique ◽

Atomic Substitution

AbstractNonlayered two-dimensional (2D) materials have attracted increasing attention, due to novel physical properties, unique surface structure, and high compatibility with microfabrication technique. However, owing to the inherent strong covalent bonds, the direct synthesis of 2D planar structure from nonlayered materials, especially for the realization of large-size ultrathin 2D nonlayered materials, is still a huge challenge. Here, a general atomic substitution conversion strategy is proposed to synthesize large-size, ultrathin nonlayered 2D materials. Taking nonlayered CdS as a typical example, large-size ultrathin nonlayered CdS single-crystalline flakes are successfully achieved via a facile low-temperature chemical sulfurization method, where pre-grown layered CdI2 flakes are employed as the precursor via a simple hot plate assisted vertical vapor deposition method. The size and thickness of CdS flakes can be controlled by the CdI2 precursor. The growth mechanism is ascribed to the chemical substitution reaction from I to S atoms between CdI2 and CdS, which has been evidenced by experiments and theoretical calculations. The atomic substitution conversion strategy demonstrates that the existing 2D layered materials can serve as the precursor for difficult-to-synthesize nonlayered 2D materials, providing a bridge between layered and nonlayered materials, meanwhile realizing the fabrication of large-size ultrathin nonlayered 2D materials.

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