Realization of nearly dispersionless bands with strong orbital anisotropy from destructive interference in twisted bilayer MoS2

AbstractRecently, the twist angle between adjacent sheets of stacked van der Waals materials emerged as a new knob to engineer correlated states of matter in two-dimensional heterostructures in a controlled manner, giving rise to emergent phenomena such as superconductivity or correlated insulating states. Here, we use an ab initio based approach to characterize the electronic properties of twisted bilayer MoS2. We report that, in marked contrast to twisted bilayer graphene, slightly hole-doped MoS2 realizes a strongly asymmetric px-py Hubbard model on the honeycomb lattice, with two almost entirely dispersionless bands emerging due to destructive interference. The origin of these dispersionless bands, is similar to that of the flat bands in the prototypical Lieb or Kagome lattices and co-exists with the general band flattening at small twist angle due to the moiré interference. We study the collective behavior of twisted bilayer MoS2 in the presence of interactions, and characterize an array of different magnetic and orbitally-ordered correlated phases, which may be susceptible to quantum fluctuations giving rise to exotic, purely quantum, states of matter.

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Realization of nearly dispersionless bands with strong orbital anisotropy from destructive interference in twisted bilayer MoS2

10.21203/rs.3.rs-125590/v1 ◽

2020 ◽

Author(s):

Lede Xian ◽

Martin Claassen ◽

Dominik Kiese ◽

Michael M. Scherer ◽

Simon Trebst ◽

...

Keyword(s):

Collective Behavior ◽

Twist Angle ◽

Quantum States ◽

Honeycomb Lattice ◽

Destructive Interference ◽

Marked Contrast ◽

Flat Bands ◽

Emergent Phenomena ◽

Twisted Bilayer Graphene ◽

Van Der Waals Materials

Abstract Recently, the twist angle between adjacent sheets of stacked van der Waals materials emerged as a new knob to engineer correlated states of matter in twodimensional heterostructures in a controlled manner, giving rise to emergent phenomena such as superconductivity or correlated insulating states. Here, we use an ab initio based approach to characterize the electronic properties of twisted bilayer MoS2. We report that, in marked contrast to twisted bilayer graphene, slightly hole-doped MoS2 realizes a strongly asymmetric px-py Hubbard model on the honeycomb lattice, with two almost entirely dispersionless bands emerging due to destructive interference. The origin of these dispersionless bands, is similar to that of the flat bands in the prototypical Lieb or Kagome lattices and co-exists with the general band flattening at small twist angle due to the Moir´e interference. We study the collective behavior of twisted bilayer MoS2 in the presence of interactions, and characterize an array of different magnetic and orbitally-ordered correlated phases, which may be susceptible to quantum fluctuations giving rise to exotic, purely quantum, states of matter.

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Hyperbolic enhancement of photocurrent patterns in minimally twisted bilayer graphene

Nature Communications ◽

10.1038/s41467-021-21792-2 ◽

2021 ◽

Vol 12 (1) ◽

Cited By ~ 2

Author(s):

S. S. Sunku ◽

D. Halbertal ◽

T. Stauber ◽

S. Chen ◽

A. S. McLeod ◽

...

Keyword(s):

Domain Walls ◽

Hexagonal Boron Nitride ◽

Twist Angle ◽

Bilayer Graphene ◽

Scanning Probe ◽

Two Dimensional ◽

Mid Infrared ◽

Two Dimensional Materials ◽

Twisted Bilayer Graphene ◽

Infrared Frequencies

AbstractQuasi-periodic moiré patterns and their effect on electronic properties of twisted bilayer graphene have been intensely studied. At small twist angle θ, due to atomic reconstruction, the moiré superlattice morphs into a network of narrow domain walls separating micron-scale AB and BA stacking regions. We use scanning probe photocurrent imaging to resolve nanoscale variations of the Seebeck coefficient occurring at these domain walls. The observed features become enhanced in a range of mid-infrared frequencies where the hexagonal boron nitride substrate is optically hyperbolic. Our results illustrate the capabilities of the nano-photocurrent technique for probing nanoscale electronic inhomogeneities in two-dimensional materials.

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Designing spin-textured ﬂat bands in twisted graphene multilayers via helimagnet encapsulation

2D Materials ◽

10.1088/2053-1583/ac4af8 ◽

2022 ◽

Author(s):

Guangze Chen ◽

Maryam Khosravian ◽

Jose Lado ◽

Aline Ramires

Keyword(s):

Helical Structure ◽

Bilayer Graphene ◽

Flat Band ◽

Two Dimensional ◽

Local Exchange ◽

Flat Bands ◽

Starting Point ◽

Twisted Bilayer Graphene ◽

Spin Texture ◽

Twisted Graphene

Abstract Twisted graphene multilayers provide tunable platforms to engineer flat bands and exploit the associated strongly correlated physics. The two-dimensional nature of these systems makes them suitable for encapsulation by materials that break specific symmetries. In this context, recently discovered two-dimensional helimagnets, such as the multiferroic monolayer NiI2, are specially appealing for breaking time-reversal and inversion symmetries due to their nontrivial spin textures. Here we show that this spin texture can be imprinted on the electronic structure of twisted bilayer graphene by proximity effect. We discuss the dependence of the imprinted spin texture on the wave-vector of the helical structure, and on the strength of the effective local exchange field. Based on these results we discuss the nature of the superconducting instabilities that can take place in helimagnet encapsulated twisted bilayer graphene. Our results put forward helimagnetic encapsulation as a powerful way of designing spin-textured flat band systems, providing a starting point to engineer a new family of correlated moire states.

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Multiple flat bands and topological Hofstadter butterfly in twisted bilayer graphene close to the second magic angle

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2100006118 ◽

2021 ◽

Vol 118 (30) ◽

pp. e2100006118

Author(s):

Xiaobo Lu ◽

Biao Lian ◽

Gaurav Chaudhary ◽

Benjamin A. Piot ◽

Giulio Romagnoli ◽

...

Keyword(s):

Condensed Matter ◽

Bilayer Graphene ◽

Band Gaps ◽

Magic Angle ◽

Two Dimensional ◽

Quantum Phases ◽

Electron Band ◽

Flat Bands ◽

Twisted Bilayer Graphene ◽

Hofstadter Butterfly

Moiré superlattices in two-dimensional van der Waals heterostructures provide an efficient way to engineer electron band properties. The recent discovery of exotic quantum phases and their interplay in twisted bilayer graphene (tBLG) has made this moiré system one of the most renowned condensed matter platforms. So far studies of tBLG have been mostly focused on the lowest two flat moiré bands at the first magic angle θm1 ∼ 1.1°, leaving high-order moiré bands and magic angles largely unexplored. Here we report an observation of multiple well-isolated flat moiré bands in tBLG close to the second magic angle θm2 ∼ 0.5°, which cannot be explained without considering electron–election interactions. With high magnetic field magnetotransport measurements we further reveal an energetically unbound Hofstadter butterfly spectrum in which continuously extended quantized Landau level gaps cross all trivial band gaps. The connected Hofstadter butterfly strongly evidences the topologically nontrivial textures of the multiple moiré bands. Overall, our work provides a perspective for understanding the quantum phases in tBLG and the fractal Hofstadter spectra of multiple topological bands.

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Photonic crystals for nano-light in moiré graphene superlattices

Science ◽

10.1126/science.aau5144 ◽

2018 ◽

Vol 362 (6419) ◽

pp. 1153-1156 ◽

Cited By ~ 69

Author(s):

S. S. Sunku ◽

G. X. Ni ◽

B. Y. Jiang ◽

H. Yoo ◽

A. Sternbach ◽

...

Keyword(s):

Graphene Layer ◽

Twist Angle ◽

Interlayer Coupling ◽

Tuning Parameter ◽

Low Loss ◽

Quantum Properties ◽

Twisted Bilayer Graphene ◽

Van Der Waals Materials ◽

Nano Imaging ◽

Plasmon Polaritons

Graphene is an atomically thin plasmonic medium that supports highly confined plasmon polaritons, or nano-light, with very low loss. Electronic properties of graphene can be drastically altered when it is laid upon another graphene layer, resulting in a moiré superlattice. The relative twist angle between the two layers is a key tuning parameter of the interlayer coupling in thus-obtained twisted bilayer graphene (TBG). We studied the propagation of plasmon polaritons in TBG by infrared nano-imaging. We discovered that the atomic reconstruction occurring at small twist angles transforms the TBG into a natural plasmon photonic crystal for propagating nano-light. This discovery points to a pathway for controlling nano-light by exploiting quantum properties of graphene and other atomically layered van der Waals materials, eliminating the need for arduous top-down nanofabrication.

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Unfolding energy spectra of double-periodicity two-dimensional systems: Twisted bilayer graphene and MoS2 on graphene

Physical Review Materials ◽

10.1103/physrevmaterials.2.010801 ◽

2018 ◽

Vol 2 (1) ◽

Cited By ~ 4

Author(s):

Yu-ichiro Matsushita ◽

Hirofumi Nishi ◽

Jun-ichi Iwata ◽

Taichi Kosugi ◽

Atsushi Oshiyama

Keyword(s):

Bilayer Graphene ◽

Energy Spectra ◽

Two Dimensional ◽

Twisted Bilayer Graphene

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Robust zero modes in disordered two-dimensional honeycomb lattice with Kekulé bond ordering

Annals of Physics ◽

10.1016/j.aop.2021.168440 ◽

2021 ◽

pp. 168440

Author(s):

Tohru Kawarabayashi ◽

Yuya Inoue ◽

Ryo Itagaki ◽

Yasuhiro Hatsugai ◽

Hideo Aoki

Keyword(s):

Honeycomb Lattice ◽

Two Dimensional ◽

Zero Modes

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Stability and superconductivity of Ca-intercalated bilayer blue phosphorene

Physical Chemistry Chemical Physics ◽

10.1039/d0cp05984f ◽

2021 ◽

Author(s):

Artur Durajski ◽

Kamil Skoczylas ◽

Radoslaw Szczesniak

Keyword(s):

Superconducting State ◽

Potential Application ◽

Recent Experiment ◽

Superconducting Devices ◽

Bilayer Graphene ◽

Two Dimensional ◽

Twisted Bilayer Graphene ◽

Blue Phosphorene

Superconductivity attracts much interest in two-dimensional compounds due to their potential application in nano-superconducting devices. Inspired by a recent experiment reporting the superconducting state in twisted bilayer graphene, here, based...

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