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

2D Materials ◽  
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.

scholarly journals Interaction effects and superconductivity signatures in twisted double-bilayer WSe2

2020 ◽  
Vol 5 (9) ◽  
pp. 1309-1316 ◽  
Author(s):  
Liheng An ◽  
Xiangbin Cai ◽  
Ding Pei ◽  
Meizhen Huang ◽  
Zefei Wu ◽  
...  
Keyword(s):  
Interaction Effects ◽  
Bilayer Graphene ◽  
Insulator Transition ◽  
Electron Interaction ◽  
Flat Band ◽  
Two Dimensional ◽  
Twisted Bilayer Graphene ◽  
Interaction Phenomena

Twisted bilayer graphene provides a new two-dimensional platform for studying electron interaction phenomena and flat band properties such as correlated insulator transition, superconductivity and ferromagnetism at certain magic angles.

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

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.

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

2018 ◽  
Vol 2 (1) ◽  
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

scholarly journals Chirality-induced spin texture switching in twisted bilayer graphene

2021 ◽  
Vol 104 (7) ◽  
Author(s):  
Kunihiro Yananose ◽  
Giovanni Cantele ◽  
Procolo Lucignano ◽  
Sang-Wook Cheong ◽  
Jaejun Yu ◽  
...  
Keyword(s):  
Bilayer Graphene ◽  
Twisted Bilayer Graphene ◽  
Spin Texture

Stability and superconductivity of Ca-intercalated bilayer blue phosphorene

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...

scholarly journals Flat bands in slightly twisted bilayer graphene: Tight-binding calculations

2010 ◽  
Vol 82 (12) ◽  
Author(s):  
E. Suárez Morell ◽  
J. D. Correa ◽  
P. Vargas ◽  
M. Pacheco ◽  
Z. Barticevic
Keyword(s):  
Tight Binding ◽  
Bilayer Graphene ◽  
Flat Bands ◽  
Twisted Bilayer Graphene

scholarly journals Extremely flat band in bilayer graphene

2018 ◽  
Vol 4 (11) ◽  
pp. eaau0059 ◽  
Author(s):  
D. Marchenko ◽  
D. V. Evtushinsky ◽  
E. Golias ◽  
A. Varykhalov ◽  
Th. Seyller ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Bilayer Graphene ◽  
Flat Band ◽  
Honeycomb Lattice ◽  
Band Model ◽  
Two Dimensional ◽  
Band Formation ◽  
Constant Energy ◽  
Mexican Hat ◽  
Band Dispersion

We propose a novel mechanism of flat band formation based on the relative biasing of only one sublattice against other sublattices in a honeycomb lattice bilayer. The mechanism allows modification of the band dispersion from parabolic to “Mexican hat”–like through the formation of a flattened band. The mechanism is well applicable for bilayer graphene—both doped and undoped. By angle-resolved photoemission from bilayer graphene on SiC, we demonstrate the possibility of realizing this extremely flattened band (< 2-meV dispersion), which extends two-dimensionally in a k-space area around the K¯ point and results in a disk-like constant energy cut. We argue that our two-dimensional flat band model and the experimental results have the potential to contribute to achieving superconductivity of graphene- or graphite-based systems at elevated temperatures.

scholarly journals Flat-band ferromagnetism in twisted bilayer graphene

2020 ◽  
Vol 102 (23) ◽  
Author(s):  
R. Pons ◽  
A. Mielke ◽  
T. Stauber
Keyword(s):  
Bilayer Graphene ◽  
Flat Band ◽  
Twisted Bilayer Graphene

scholarly journals Moiré with flat bands is different

2019 ◽  
Vol 50 (3) ◽  
pp. 24-26
Author(s):  
Tero T. Heikkilä ◽  
Timo Hyart
Keyword(s):  
Critical Temperature ◽  
Fermi Surface ◽  
Room Temperature ◽  
Electronic States ◽  
Bilayer Graphene ◽  
Flat Bands ◽  
Twisted Bilayer Graphene

Recent experimental discoveries of superconductivity and other exotic electronic states in twisted bilayer graphene (TBG) call for a reconsideration of our traditional theories of these states, usually based on the assumption of the presence of a Fermi surface. Here we show how such developments may even help us finding mechanisms of increasing the critical temperature of superconductivity towards the room temperature.

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