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 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 Fast pick up technique for high quality heterostructures of bilayer graphene and hexagonal boron nitride

2014 ◽  
Vol 105 (1) ◽  
pp. 013101 ◽  
Author(s):  
P. J. Zomer ◽  
M. H. D. Guimarães ◽  
J. C. Brant ◽  
N. Tombros ◽  
B. J. van Wees
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
Bilayer Graphene ◽  
High Quality

scholarly journals 2D-3D integration of hexagonal boron nitride and a high-κ dielectric for ultrafast graphene-based electro-absorption modulators

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hitesh Agarwal ◽  
Bernat Terrés ◽  
Lorenzo Orsini ◽  
Alberto Montanaro ◽  
Vito Sorianello ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Hafnium Oxide ◽  
High Speed ◽  
Hexagonal Boron Nitride ◽  
Temperature Stability ◽  
Cost Effective ◽  
Fold Increase ◽  
Building Blocks ◽  
High Quality ◽  
New Device

AbstractElectro-absorption (EA) waveguide-coupled modulators are essential building blocks for on-chip optical communications. Compared to state-of-the-art silicon (Si) devices, graphene-based EA modulators promise smaller footprints, larger temperature stability, cost-effective integration and high speeds. However, combining high speed and large modulation efficiencies in a single graphene-based device has remained elusive so far. In this work, we overcome this fundamental trade-off by demonstrating the 2D-3D dielectric integration in a high-quality encapsulated graphene device. We integrated hafnium oxide (HfO2) and two-dimensional hexagonal boron nitride (hBN) within the insulating section of a double-layer (DL) graphene EA modulator. This combination of materials allows for a high-quality modulator device with high performances: a ~39 GHz bandwidth (BW) with a three-fold increase in modulation efficiency compared to previously reported high-speed modulators. This 2D-3D dielectric integration paves the way to a plethora of electronic and opto-electronic devices with enhanced performance and stability, while expanding the freedom for new device designs.

scholarly journals Facile Synthesis of High-Quality Nano-Size 10B-Enriched Fibers of Hexagonal Boron Nitride

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 222
Author(s):  
Pervaiz Ahmad ◽  
Mayeen Uddin Khandaker ◽  
Fida Rehman ◽  
Nawshad Muhammad ◽  
Mohammad Rashed Iqbal Faruque ◽  
...  
Keyword(s):  
Boron Nitride ◽  
High Intensity ◽  
Hexagonal Boron Nitride ◽  
Internal Space ◽  
Facile Synthesis ◽  
High Quality ◽  
Crystalline Nature ◽  
Nano Size ◽  
Advanced Applications

The interesting properties of hexagonal boron nitride (h-BN) and its potential uses in thermo-structural advanced applications have been limited or restricted by its inherent brittleness, which can easily be eliminated by its fibers (h-BN) in nanoscale dimensions. The current study is based on the synthesis of nanoscale 10B-enriched fibers of h-BN (10BNNFs) from 10B in the precursors instead of B in two-hour annealing at 900 °C and one-hour growth at 1000 °C. All of the 10BNNFs are randomly curved and highly condensed or filled from 10h-BN species with no internal space or crack. XRD peaks reported the 10h-BN phase and highly crystalline nature of the synthesized 10BNNFs. 10h-BN phase and crystalline nature of 10BNNFs are confirmed from high-intensity peaks at 1392 (cm−1) in Raman and FTIR spectroscopes.

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

scholarly journals Chemical potential and quantum Hall ferromagnetism in bilayer graphene

Science ◽  
2014 ◽  
Vol 345 (6192) ◽  
pp. 58-61 ◽  
Author(s):  
Kayoung Lee ◽  
Babak Fallahazad ◽  
Jiamin Xue ◽  
David C. Dillen ◽  
Kyounghwan Kim ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Chemical Potential ◽  
Hexagonal Boron Nitride ◽  
Quantum Hall ◽  
Bilayer Graphene ◽  
Zero Magnetic Field ◽  
High Magnetic Fields ◽  
Complex Interplay ◽  
Electron Hole ◽  
Quantum Hall State

Bilayer graphene has a distinctive electronic structure influenced by a complex interplay between various degrees of freedom. We probed its chemical potential using double bilayer graphene heterostructures, separated by a hexagonal boron nitride dielectric. The chemical potential has a nonlinear carrier density dependence and bears signatures of electron-electron interactions. The data allowed a direct measurement of the electric field–induced bandgap at zero magnetic field, the orbital Landau level (LL) energies, and the broken-symmetry quantum Hall state gaps at high magnetic fields. We observe spin-to-valley polarized transitions for all half-filled LLs, as well as emerging phases at filling factors ν = 0 and ν = ±2. Furthermore, the data reveal interaction-driven negative compressibility and electron-hole asymmetry in N = 0, 1 LLs.

Generation of High-Density Quantum Emitters in High-Quality, Exfoliated Hexagonal Boron Nitride

2021 ◽  
Vol 13 (39) ◽  
pp. 47283-47292
Author(s):  
Yongliang Chen ◽  
Chi Li ◽  
Simon White ◽  
Milad Nonahal ◽  
Zai-Quan Xu ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
High Density ◽  
High Quality ◽  
Quantum Emitters

Synthesis of centimeter-scale high-quality polycrystalline hexagonal boron nitride films from the Fe flux

Nanoscale ◽  
2021 ◽  
Author(s):  
Yifei Li ◽  
Xin Wen ◽  
Changjie Tan ◽  
Ning Li ◽  
Ruijie Li ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
Two Dimensional ◽  
High Quality ◽  
Boron Nitride Films

Owing to its irreplaceable roles in new functional devices, such as universal substrates and excellent layered insulators, high-quality hexagonal BN (hBN) crystals are exceedingly required in the field of two-dimensional...

Self-catalyzed VLS growth of PbSe wires with significant suppression of the VS process

CrystEngComm ◽  
2018 ◽  
Vol 20 (35) ◽  
pp. 5269-5274 ◽  
Author(s):  
Chao Fan ◽  
Xing Xu ◽  
Yushuang Zhang ◽  
Tianren Chen ◽  
Songyang Wang ◽  
...  
Keyword(s):  
Infrared Emission ◽  
Significant Suppression ◽  
High Quality ◽  
Mid Infrared ◽  
Controllable Growth ◽  
Vls Growth

Controllable growth of high-quality PbSe wires with strong mid-infrared emission was achieved with significant suppression of the vapor–solid-grown cubes.

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