scholarly journals Hyperbolic enhancement of photocurrent patterns in minimally twisted bilayer graphene

2021 ◽  
Vol 12 (1) ◽  
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.

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

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 Evidence of Orbital Ferromagnetism in Twisted Bilayer Graphene Aligned to Hexagonal Boron Nitride

Nano Letters ◽  
2021 ◽  
Author(s):  
Aaron L. Sharpe ◽  
Eli J. Fox ◽  
Arthur W. Barnard ◽  
Joe Finney ◽  
Kenji Watanabe ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
Bilayer Graphene ◽  
Twisted Bilayer Graphene

Tunable excitons in bilayer graphene

Science ◽  
2017 ◽  
Vol 358 (6365) ◽  
pp. 907-910 ◽  
Author(s):  
Long Ju ◽  
Lei Wang ◽  
Ting Cao ◽  
Takashi Taniguchi ◽  
Kenji Watanabe ◽  
...  
Keyword(s):  
Bound States ◽  
Hexagonal Boron Nitride ◽  
Solid Material ◽  
Bilayer Graphene ◽  
Winding Number ◽  
Narrow Line ◽  
High Quality ◽  
Mid Infrared ◽  
Photocurrent Spectroscopy ◽  
Line Widths

Excitons, the bound states of an electron and a hole in a solid material, play a key role in the optical properties of insulators and semiconductors. Here, we report the observation of excitons in bilayer graphene (BLG) using photocurrent spectroscopy of high-quality BLG encapsulated in hexagonal boron nitride. We observed two prominent excitonic resonances with narrow line widths that are tunable from the mid-infrared to the terahertz range. These excitons obey optical selection rules distinct from those in conventional semiconductors and feature an electron pseudospin winding number of 2. An external magnetic field induces a large splitting of the valley excitons, corresponding to a g-factor of about 20. These findings open up opportunities to explore exciton physics with pseudospin texture in electrically tunable graphene systems​.

scholarly journals Electronic Properties of Twisted Bilayer Graphene in the Presence of a Magnetic Field

2020 ◽  
Vol 233 ◽  
pp. 03004
Author(s):  
M.F.C. Martins Quintela ◽  
J.C.C. Guerra ◽  
S.M. João
Keyword(s):  
Magnetic Field ◽  
Electronic Properties ◽  
Twist Angle ◽  
Bilayer Graphene ◽  
Polynomial Method ◽  
Zero Energy ◽  
Energy Bands ◽  
Optical And Electronic Properties ◽  
Twisted Bilayer Graphene ◽  
Kernel Polynomial Method

In AA-stacked twisted bilayer graphene, the lower energy bands become completely flat when the twist angle passes through certain specific values: the so-called “magic angles”. The Dirac peak appears at zero energy due to the flattening of these bands when the twist angle is sufficiently small [1-3]. When a constant perpendicular magnetic field is applied, Landau levels start appearing as expected [5]. We used the Kernel Polynomial Method (KPM) [6] as implemented in KITE [7] to study the optical and electronic properties of these systems. The aim of this work is to analyze how the features of these quantities change with the twist angle in the presence of an uniform magnetic field.

scholarly journals Steering the current flow in twisted bilayer graphene

2022 ◽  
Author(s):  
Jesús Arturo Sánchez-Sánchez ◽  
Montserrat Navarro-Espino ◽  
Yonatan Betancur Ocampo ◽  
José Eduardo Barrios Vargas ◽  
Thomas Stegmann
Keyword(s):  
Current Flow ◽  
Twist Angle ◽  
Bottom Layer ◽  
Bilayer Graphene ◽  
Energy Bands ◽  
Initial Direction ◽  
Steering Angle ◽  
Graphene Layers ◽  
Ballistic Electron ◽  
Twisted Bilayer Graphene

Abstract A nanoelectronic device made of twisted bilayer graphene (TBLG) is proposed to steer the direction of the current flow. The ballistic electron current, injected at one edge of the bottom layer, can be guided predominantly to one of the lateral edges of the top layer. The current is steered to the opposite lateral edge, if either the twist angle is reversed or the electrons are injected in the valence band instead of the conduction band, making it possible to control the current flow by electric gates. When both graphene layers are aligned, the current passes straight through the system without changing its initial direction. The observed steering angle exceeds well the twist angle and emerges for a broad range of experimentally accessible parameters. It is explained by the twist angle and the trigonal shape of the energy bands beyond the van Hove singularity due to the Moiré interference pattern. As the shape of the energy bands depends on the valley degree of freedom, the steered current is valley polarized. Our findings show how to control and manipulate the current flow in TBLG. Technologically, they are of relevance for applications in twistronics and valleytronics.

scholarly journals Carrier transport theory for twisted bilayer graphene in the metallic regime

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Girish Sharma ◽  
Indra Yudhistira ◽  
Nilotpal Chakraborty ◽  
Derek Y. H. Ho ◽  
M. M. Al Ezzi ◽  
...  
Keyword(s):  
Experimental Data ◽  
Carrier Transport ◽  
Transport Theory ◽  
Phonon Scattering ◽  
Twist Angle ◽  
Quantitative Agreement ◽  
Bilayer Graphene ◽  
Magic Angle ◽  
Accurate Treatment ◽  
Twisted Bilayer Graphene

AbstractUnderstanding the normal-metal state transport in twisted bilayer graphene near magic angle is of fundamental importance as it provides insights into the mechanisms responsible for the observed strongly correlated insulating and superconducting phases. Here we provide a rigorous theory for phonon-dominated transport in twisted bilayer graphene describing its unusual signatures in the resistivity (including the variation with electron density, temperature, and twist angle) showing good quantitative agreement with recent experiments. We contrast this with the alternative Planckian dissipation mechanism that we show is incompatible with available experimental data. An accurate treatment of the electron-phonon scattering requires us to go well beyond the usual treatment, including both intraband and interband processes, considering the finite-temperature dynamical screening of the electron-phonon matrix element, and going beyond the linear Dirac dispersion. In addition to explaining the observations in currently available experimental data, we make concrete predictions that can be tested in ongoing experiments.

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