Article
Optics
Yupei Wang, Jian Wei You, Nicolae C. Panoiu
Summary: We show that the Kerr effect on valley-Hall topological transport in graphene metasurfaces can be utilized to achieve an all-optical switch. By utilizing the high Kerr coefficient of graphene, the refractive index of the topologically-protected metasurface can be tuned by a pump beam, resulting in an optically controllable frequency shift of the photonic bands. This spectral variation enables the control and switching of optical signals in specific waveguide modes of the graphene metasurface. The dependence of the threshold pump power on the group velocity of the pump mode, especially in the slow-light regime, is crucial for the optical switching.
Article
Materials Science, Multidisciplinary
Ahmal Jawad Zafar, Aranyo Mitra, Vadym Apalkov
Summary: In this study, the electron dynamics of a graphene nanoring in the presence of an ultrashort optical pulse were theoretically investigated. It was found that circularly polarized pulses can induce valley polarization in the graphene nanoring, whereas no valley polarization is observed in a graphene monolayer. The magnitude of the valley polarization in the graphene nanoring depends on the system parameters.
Article
Multidisciplinary Sciences
S. E. Krasavin, V. A. Osipov
Summary: This study reveals the decisive role of grain-boundary-induced strain fields in electron scattering in polycrystalline graphene, and proposes a model to explain the effect of the microscopic structure of grain boundaries on the electrical resistivity.
SCIENTIFIC REPORTS
(2022)
Article
Multidisciplinary Sciences
Xiang Gao, Wengen Ouyang, Michael Urbakh, Oded Hod
Summary: The investigation of corrugated grain boundaries on the frictional properties of extended planar graphitic contacts reveals a nonmonotonic behavior in friction due to dynamic buckling effects. The resulting negative differential friction coefficients can reduce linear scaling of grain-boundary friction with surface area and restore structural superlubricity at increasing length scales. Achieving ultra-low friction at macroscopic scales is highly desirable.
NATURE COMMUNICATIONS
(2021)
Article
Materials Science, Multidisciplinary
Antonio L. R. Manesco, Jose L. Lado
Summary: Research shows that in buckled graphene superlattices, long-range electronic correlations lead to a competition between antiferromagnetic and charge density wave instabilities, which can be controlled through screening engineering. This results in the emergence of a topologically non-trivial quantum valley Hall insulating state.
Article
Materials Science, Multidisciplinary
Fionnuala Solomon, Stephen R. Power
Summary: Intrinsic and extrinsic valley Hall effects are predicted to emerge in graphene systems, with strong valley-dependent scattering observed in bilayer graphene quantum dots. Custom mass profiles in bilayer graphene devices provide an excellent platform for future exploration of valleytronic phenomena in two-dimensional materials.
Article
Physics, Fluids & Plasmas
Zihua Liu, Debabrata Panja, Gerard T. Barkema
Summary: The mechanical properties of graphene were studied through computer simulations and their connection to experimental results was made. The study found that graphene's area and aspect ratio exhibit diffusive behavior over short timescales, with diffusion coefficients that are related. Fluctuations in area are bounded over longer timescales, while those in aspect ratio are not. The dynamic behavior of polycrystalline graphene under external forces can also be derived from the diffusion coefficients, and the diffusion coefficients depend on the structural properties of the material.
Article
Materials Science, Multidisciplinary
A. Friedlan, M. M. Dignam
Summary: This paper presents a detailed theoretical study of valley polarization in biased bilayer graphene, showing that nearly perfect valley polarization can be achieved with the proper choices of external bias and pulse frequency. Valley polarization originates from a ring of states surrounding each rather than from the Dirac points, and intervalley scattering and thermal populations can greatly reduce valley polarization. This work provides insight into the origin of valley polarization in bilayer graphene and will help experimentalists studying valley polarization in the laboratory.
Article
Chemistry, Multidisciplinary
Federico D'Ambrosio, Joris Barkema, Gerard T. Barkema
Summary: Experimentally produced graphene samples are often polycrystalline, and realistic computer samples are needed for study. A new method has been introduced for faster relaxation of the material and a tool to remove unwanted artifacts.
Article
Chemistry, Multidisciplinary
Henry Yu, Alex Kutana, Boris Yakobson
Summary: In this paper, we demonstrate the use of substrate topography to induce static pseudo-electromagnetic (EM) fields in graphene and study their effects on electron motion. Through trajectory analysis, we design various optical devices and propose a setup to achieve the valley Hall effect solely through substrate patterning. We also discuss the experimental verification of strain/pseudo-EM field patterns and their generalization to other 2D materials.
Article
Materials Science, Multidisciplinary
Glenn Packard, Carolyn Spaulding, Alex Taylor, Karl Hirschman, Scott Williams, Santosh Kurinec
Summary: Doping of thin amorphous silicon on glass substrate was achieved using Monolayer doping via Flash Lamp Annealing, resulting in the formation of n+ polycrystalline silicon in selective regions. The process successfully demonstrated the fabrication of N-channel field effect transistor devices.
Article
Optics
M. S. Mrudul, Gopal Dixit
Summary: This study focuses on optimizing valley polarization in monolayer graphene by controlling different laser parameters, with the goal of enabling logical operations in two-dimensional materials. Another approach using linearly polarized laser pulses is also explored to induce significant valley polarization in graphene, helping experimentalists choose a suitable method to achieve desired control over valley polarization.
JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Chuyao Tong, Rebekka Garreis, Angelika Knothe, Marius Eich, Agnese Sacchi, Kenji Watanabe, Takashi Taniguchi, Vladimir Fal'ko, Thomas Ihn, Klaus Ensslin, Annika Kurzmann
Summary: Quantum states in graphene have two-fold degeneracy in spins and valleys, which can be utilized for qubit preparations. In bilayer graphene quantum dots, the valley g-factor can be tuned by gate voltage adjustments, resulting in larger g-factor with larger electronic dot sizes. Bipolar operation on the versatile device allows for the observation of transitions from electron dots to hole dots. Addition of gates can extend the system to host tunable double dots.
Article
Optics
Soojeong Baek, Sang Hyun Park, Donghak Oh, Kanghee Lee, Sangha Lee, Hosub Lim, Taewoo Ha, Hyun Sung Park, Shuang Zhang, Lan Yang, Bumki Min, Teun-Teun Kim
Summary: In this study, an electrical and spectral method is proposed to resolve chiral exceptional points (EPs) and clarify the consequences of chiral mode collapsing in a non-Hermitian gated graphene metasurface. The measured non-Hermitian Jones matrix in parameter space enables the quantification of nonorthogonality and topological charges associated with a chiral EP. The results show that electrically controllable non-Hermitian metasurface platforms can provide insights into rich non-Hermitian polarisation dynamics around chiral EPs.
LIGHT-SCIENCE & APPLICATIONS
(2023)
Article
Physics, Applied
Ruigang Li, Jun-Feng Liu, Jun Wang
Summary: We propose using strain to achieve perfect valley precession, which creates an effective vector potential and moves two valleys in opposite directions in momentum space. The spatial period of precession is independent of Fermi energy and transverse wave vector, making it crucial for practical devices with multiple transverse wave vectors or modes. By investigating the conductivity of a Kekule graphene superlattice/graphene/Kekule graphene superlattice junction, we theoretically demonstrate perfect valley precession, with conductivity exhibiting perfect oscillations and minimal values close to zero. This finding offers a strategy for designing ideal valleytronics and straintronics devices.
PHYSICAL REVIEW APPLIED
(2023)
Article
Materials Science, Multidisciplinary
V. Hung Nguyen, J-C Charlier
Article
Chemistry, Multidisciplinary
Riju Banerjee, Viet-Hung Nguyen, Tomotaroh Granzier-Nakajima, Lavish Pabbi, Aurelien Lherbier, Anna Ruth Binion, Jean-Christophe Charlier, Mauricio Terrones, Eric William Hudson
Article
Materials Science, Multidisciplinary
B. Brun, N. Moreau, S. Somanchi, V-H Nguyen, A. Mrenca-Kolasinska, K. Watanabe, T. Taniguchi, J-C Charlier, C. Stampfer, B. Hackens
Review
Chemistry, Multidisciplinary
Aurelie Champagne, Samuel Dechamps, Simon M. -M. Dubois, Aurelien Lherbier, Viet-Hung Nguyen, Jean-Christophe Charlier
APPLIED SCIENCES-BASEL
(2020)
Article
Multidisciplinary Sciences
Andreij C. Gadelha, Douglas A. A. Ohlberg, Cassiano Rabelo, Eliel G. S. Neto, Thiago L. Vasconcelos, Joao L. Campos, Jessica S. Lemos, Vinicius Ornelas, Daniel Miranda, Rafael Nadas, Fabiano C. Santana, Kenji Watanabe, Takashi Taniguchi, Benoit van Troeye, Michael Lamparski, Vincent Meunier, Viet-Hung Nguyen, Dawid Paszko, Jean-Christophe Charlier, Leonardo C. Campos, Luiz G. Cancado, Gilberto Medeiros-Ribeiro, Ado Jorio
Summary: The twisted bilayer graphene undergoes self-organized lattice reconstruction, resulting in the formation of a superlattice that modulates vibrational and electronic structures, leading to phenomena such as strong correlations and superconductivity. Although experimental techniques and theoretical models face challenges in observing and describing these effects, nano-Raman spectroscopy can localize some vibrational modes and provide insights into the effects of electron-phonon coupling on the material properties.
Article
Materials Science, Multidisciplinary
V. Hung Nguyen, D. Paszko, M. Lamparski, B. Van Troeye, V Meunier, J-C Charlier
Summary: This study demonstrates that small-angle twisted bilayer graphene systems exhibit significant electron localization, but for twist angles below 1.1 degrees, the contribution of the local AA regions is progressively reduced, thus preventing the emergence of further magic angles.
Article
Chemistry, Multidisciplinary
Boris Brun, Viet-Hung Nguyen, Nicolas Moreau, Sowmya Somanchi, Kenji Watanabe, Takashi Taniguchi, Jean-Christophe Charlier, Christoph Stampfer, Benoit Hackens
Summary: When confined in circular cavities, graphene charge carriers occupy whispering gallery modes (WGMs) similarly to classical acoustic and optical fields. The study successfully demonstrated the transduction of WGMs to the outside world through a novel configuration, showing mode selectivity and potential for designing disruptive quantum devices. This work provides a proof of concept for graphene whisperitronic devices.
Article
Chemistry, Multidisciplinary
Mustafa Neset Cinar, Aleandro Antidormi, Viet-Hung Nguyen, Alessandro Kovtun, Samuel Lara-Avila, Andrea Liscio, Jean-Christophe Charlier, Stephan Roche, Haldun Sevincli
Summary: A study reveals the charge conduction laws in multilayer reduced graphene oxides (rGO), showing that interlayer interaction and film thickness have effects on diffusion. In contacted films, conduction is predominantly driven by interlayer hopping when the mean free path becomes shorter than the channel length. These findings contribute to the optimization of graphene-based composites with improved electrical conduction.
Article
Chemistry, Multidisciplinary
Andreij C. Gadelha, Viet-Hung Nguyen, Eliel G. S. Neto, Fabiano Santana, Markus B. Raschke, Michael Lamparski, Vincent Meunier, Jean-Christophe Charlier, Ado Jorio
Summary: This study investigates the importance of phonons in twisted-bilayer graphene at the magic-angle using gate-dependent micro-Raman spectroscopy. The results reveal that the unique electronic structure at the magic-angle influences the electron-phonon coupling, resulting in a larger G band line width.
Article
Materials Science, Multidisciplinary
L. Caputo, V. -H. Nguyen, J. -C. Charlier
Summary: This study investigates the periodic doping of graphene with borazine-like rings using first-principles techniques to search for a new class of BNC hybrid 2D materials. The results show that BN-ring doped graphene materials exhibit high stabilities and optimized band gaps, making them potential candidates for optoelectronic devices.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Engineering, Electrical & Electronic
V. Hung Nguyen, J. -c. Charlier
Summary: The Green's function method is widely used in modelling quantum transport in nanoscale electronic devices. To optimize the computation cost, numerical methods and algorithms, such as recursive techniques, have been developed. However, numerical difficulty issues arise when applying these techniques to large superlattice systems. This article proposes improvements to solve these issues and demonstrates the efficiency of the method using twisted bilayer graphene superlattices.
JOURNAL OF COMPUTATIONAL ELECTRONICS
(2023)
Article
Chemistry, Multidisciplinary
Alessandra Canetta, Sergio Gonzalez-Munoz, Viet-Hung Nguyen, Khushboo Agarwal, Pauline de Crombrugghe de Picquendaele, Yuanzhuo Hong, Sambit Mohapatra, Kenji Watanabe, Takashi Taniguchi, Bernard Nysten, Benoit Hackens, Rebeca Ribeiro-Palau, Jean-Christophe Charlier, Oleg Victor Kolosov, Jean Spiece, Pascal Gehring
Summary: Using Ultrasonic Force Microscopy (UFM), researchers have quantified the variation of out-of-plane Young's modulus in minimally twisted double bilayer graphene (TDBG). They found a softening of the Young's modulus by 7% and 17% along single and double domain walls, respectively. This study highlights the tunability of nanomechanical properties in engineered twisted materials and opens new possibilities for future applications of designer 2D nanomechanical systems.
Article
Materials Science, Multidisciplinary
V. Hung Nguyen, Trinh X. Hoang, J-C Charlier
Summary: This paper presents a comprehensive and systematic study on the electronic properties of twisted multilayer graphene (TMG) through atomistic calculations. The dependence of electronic quantities on the twist angle and stacking configuration is analyzed, taking into account atomic reconstruction effects. The correlation between structural and electronic properties is clarified, highlighting the shared characteristics and differences between various TMG systems, and providing possibilities for further developments in the field of twistronics.
JOURNAL OF PHYSICS-MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
B. Brun, N. Moreau, S. Somanchi, V-H Nguyen, K. Watanabe, T. Taniguchi, J-C Charlier, C. Stampfer, B. Hackens
Article
Chemistry, Multidisciplinary
V Hung Nguyen, J-C Charlier
NANOSCALE ADVANCES
(2020)
