Article
Nanoscience & Nanotechnology
Jinglan Liu, Chunhua Zhu, Zilong Zhang, Qiancheng Ren, Xuewei Zhang, Yang Zhang, Yanhan Jin, Wei Qiu, Hongtao Wang, Junhua Zhao, Pei Zhao
Summary: This study investigates the interfacial shear coupling (ISC) of layered 2D van der Waals (vdW) materials using bilayer graphene (BLG) and isotope-labeled Raman spectroscopy. The results reveal an inverse proportionality between the interfacial shear strength and the sample size, with the ISC undergoing bonding, sliding, and debonding processes under uniaxial tensile strain. Molecular dynamics simulations attribute this inverse proportionality to the stronger interlayer vdW interaction induced by the edge lattices and atoms of BLG. These findings provide fundamental insights into the macroscopic interfacial shear properties of 2D vdW stacks and have potential applications in guiding the design of graphene-based composite materials and flexible 2D electronics.
NPJ 2D MATERIALS AND APPLICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Xutao Wang, Ningning Liu, Yanfu Wu, Yueqiao Qu, Wenxuan Zhang, Jinyue Wang, Dandan Guan, Shiyong Wang, Hao Zheng, Yaoyi Li, Canhua Liu, Jinfeng Jia
Summary: Metal-intercalated bilayer graphene has a high density of states near the Fermi energy, and thus is expected to exhibit enhanced strong correlation effect and superconductivity. By using a scanning tunneling microscope, researchers observed the superconducting energy gap and diamagnetic response in Ca-intercalated bilayer graphene, revealing strong coupling superconductivity and an isotropic s-wave superconductor.
Article
Chemistry, Physical
Thi My Duyen Huynh, Guo-Song Hung, Godfrey Gumbs, Ngoc Thanh Thuy Tran
Summary: In this study, first-principles calculations are used to investigate the feature-rich properties of alkali-metal intercalated graphene nanoribbons (GNRs), including edge passivation, stacking configurations, intercalation sites, stability, charge density distribution, magnetic configuration, and electronic properties. The findings demonstrate a transformation from finite gap semiconducting to metallic behaviors, indicating enhanced electrical conductivity. This transformation is attributed to the cooperative or competitive relations among the significant chemical bonds, finite-size quantum confinement, edge structure, and stacking order. The decoration of edge structures with hydrogen and oxygen atoms provides additional information about stability and magnetization due to the ribbons' effect.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Xujing Ji, Degong Ding, Xiaoxiao Guan, Chunyang Wu, Haofu Qian, Juexian Cao, Jixue Li, Chuanhong Jin
Summary: This study used experimental and theoretical methods to investigate the lithium intercalation induced phase transition in bilayer MoS2, revealing a correlation between the phase transition mode and stacking orders. The findings contribute to the understanding of phase transition mechanisms in 2D materials and advance the precise control of phase engineering in 2D materials for memory applications.
Article
Multidisciplinary Sciences
Myungchul Oh, Kevin P. Nuckolls, Dillon Wong, Ryan L. Lee, Xiaomeng Liu, Kenji Watanabe, Takashi Taniguchi, Ali Yazdani
Summary: Recent studies on magic-angle twisted bilayer graphene (MATBG) have shown that the superconductivity in MATBG may not be described by the conventional BCS theory, but rather resembles a non-BCS mechanism due to the large density of states in its flat bands. This suggests that the pairing mechanism in MATBG may be unconventional and different from that of conventional superconductors.
Article
Materials Science, Multidisciplinary
Guodong Yu, Yunhua Wang, Mikhail Katsnelson, Hai-Qing Lin, Shengjun Yuan
Summary: The researchers use symmetry and group representation theory to reveal the interlayer hybridization selection rules in untwisted and twisted bilayer graphene. The energy-dependent hybridization strengths in graphene quasicrystal and twisted bilayer graphene show specific characteristics, which are verified by the calculated optical conductivity spectra.
Article
Chemistry, Multidisciplinary
Qiunan Liu, Yung-Chang Lin, Silvan Kretschmer, Mahdi Ghorbani-Asl, Pablo Solis-Fernandez, Ming-Deng Siao, Po-Wen Chiu, Hiroki Ago, Arkady V. Krasheninnikov, Kazu Suenaga
Summary: This study investigates the atomic structural transformation of molybdenum(V) chloride after intercalation into bilayer graphene. The results reveal giant lattice distortions and frequent structural transitions in the intercalated material, which have never been observed in metal chloride systems. The findings deepen our understanding of matter behavior in confined spaces and provide insights for more efficient tuning of material properties through intercalation.
Article
Chemistry, Physical
Xian Wang, Mingli Yang
Summary: The interaction at the interface of two layers in twist bilayer graphene and its quantum dots varies with twist angle, with charge transfer interaction dominating the variation. This understanding of the interlayer interaction nature can lead to new approaches of optoelectronic modulation of graphene-based materials.
APPLIED SURFACE SCIENCE
(2022)
Article
Materials Science, Multidisciplinary
Xian Wang, Li Zhang, Shengping Yu, Mingli Yang, Koblar Alan Jackson
Summary: This study evaluates interlayer polarizability by computing field-induced electron density variations in twisted bilayer graphene quantum dots, revealing enhanced interlayer coupling at small and size-dependent twist angles. It provides a method for measuring interlayer electronic coupling strength in BLG.
Article
Physics, Multidisciplinary
D. A. Bandurin, A. Principi, I. Y. Phinney, T. Taniguchi, K. Watanabe, P. Jarillo-Herrero
Summary: This study demonstrates that small-angle twisted bilayer graphene provides a highly tunable system for exploring interactions-limited electron conduction. Through the development of e-h drag theory, we reveal strong mutual friction between electrons and holes and clarify the conduction mechanisms in charge-neutral SATBG.
PHYSICAL REVIEW LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Tobias Huempfner, Felix Otto, Roman Forker, Paul Mueller, Torsten Fritz
Summary: The intercalation of potassium into epitaxial bilayer graphene is shown to enable superconductivity with a critical temperature of Tc = 3.6 +/- 0.1 K. The physical mechanisms are analyzed in detail using scanning tunneling microscopy and angle-resolved photoelectron spectroscopy. The data suggest that electron-phonon coupling is the driving force for superconductivity, and multiple energy gaps are observed. Additionally, the low-dimensional effects lead to a gap ratio exceeding the BCS value for conventional superconductors. These findings highlight the significance of reduced dimensionality in determining the superconducting properties of K-intercalated epitaxial bilayer graphene.
ADVANCED MATERIALS INTERFACES
(2023)
Article
Multidisciplinary Sciences
Girish Sharma, Indra Yudhistira, Nilotpal Chakraborty, Derek Y. H. Ho, M. M. Al Ezzi, Michael S. Fuhrer, Giovanni Vignale, Shaffique Adam
Summary: The theory of phonon-dominated transport in twisted bilayer graphene explains experimental observations and contrasts with the Planckian dissipation mechanism, shedding light on the mechanisms responsible for the strongly correlated insulating and superconducting phases. Accurate treatment of electron-phonon scattering beyond the usual methods provides insights and concrete predictions for ongoing experiments.
NATURE COMMUNICATIONS
(2021)
Article
Materials Science, Multidisciplinary
Xi Wu, Fawei Zheng, Feiyu Kang, Jia Li
Summary: By using density functional theory calculations, we have identified the stable intercalated structure and the evolution of band structures in the intercalation process of Li into bilayer graphene. Our work shows that the Dirac cone of bilayer graphene can be modulated by using the generalized N/ N/ Kekule order, which opens a gap or splits the electron and hole pocket, contributed by the Kekule-O and Kekule-Y distortion respectively. This study provides valuable insights for the investigation of Li-intercalated bilayer graphene in experiments.
Article
Materials Science, Multidisciplinary
Yuki Fukaya, Yuhao Zhao, Hyun-Woo Kim, Joung Real Ahn, Hirokazu Fukidome, Iwao Matsuda
Summary: The study reveals that a precisely 30-degree twisted bilayer graphene forms a quasicrystal structure on a SiC(0001) substrate, with an interlayer distance of 3.46 angstrom that is 0.17 angstrom larger than that of Bernal-stacked bilayer graphene. This finding provides important insights into the magnitude of coupling between graphene layers.
Article
Chemistry, Multidisciplinary
Youngwook Kim, Pilkyung Moon, Kenji Watanabe, Takashi Taniguchi, Jurgen H. Smet
Summary: The study investigates the quantum Hall effect in two stacked graphene layers rotated by 2 degrees. It found that the tunneling strength among the layers can be varied from weak to strong via the mechanism of magnetic breakdown when tuning the density. The presence of odd-integer quantum Hall physics in the regime of suppressed tunneling for balanced layer densities suggests the role of Coulomb interaction induced interlayer coherence and Bose-Einstein condensation of excitons.
Article
Physics, Multidisciplinary
Ikuko Watanabe, Seigo Souma, Kosuke Nakayama, Katsuaki Sugawara, Chi Xuan Trang, Kouji Segawa, Kunihiko Yamauchi, Tamio Oguchi, Takashi Takahashi, Takafumi Sato
Summary: Realizing topological superconductors with Majorana fermions is a thrilling challenge in materials science. Researchers propose a system, Pb(111)/Bi(111) heterostructure, which has the potential to access both 1D and 2D TSCs. They observe the evolution of electronic states with varying Bi-layer thickness and demonstrate proximity-induced superconductivity in Bi(111) on a Pb(111) film.
PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS
(2022)
Article
Physics, Multidisciplinary
Kosuke Nakayama, Yongkai Li, Takemi Kato, Min Liu, Zhiwei Wang, Takashi Takahashi, Yugui Yao, Takafumi Sato
Summary: Successful electron doping to CsV3Sb5 by Cs dosing has been achieved, and the electron filling of the Sb 5p(z) and V 3d(xz/yz) bands can be selectively increased while suppressing the CDW. This result reveals the crucial role of multiorbital effect in CDW and superconductivity.
Article
Instruments & Instrumentation
Miho Kitamura, Seigo Souma, Asuka Honma, Daisuke Wakabayashi, Hirokazu Tanaka, Akio Toyoshima, Kenta Amemiya, Tappei Kawakami, Katsuaki Sugawara, Kosuke Nakayama, Kohei Yoshimatsu, Hiroshi Kumigashira, Takafumi Sato, Koji Horiba
Summary: Micro-angle-resolved photoemission spectroscopy is a powerful tool for elucidating key electronic states of exotic quantum materials, and the system developed in this study, based on Kirkpatrick-Baez mirror optics, enables accurate spatially resolved band-structure mapping.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2022)
Article
Chemistry, Multidisciplinary
Katsuaki Sugawara, Haruki Kusaka, Tappei Kawakami, Koki Yanagizawa, Asuka Honma, Seigo Souma, Kosuke Nakayama, Masashi Miyakawa, Takashi Taniguchi, Miho Kitamura, Koji Horiba, Hiroshi Kumigashira, Takashi Takahashi, Shin-ichi Orimo, Masayuki Toyoda, Susumu Saito, Takahiro Kondo, Takafumi Sato
Summary: Boron-based two-dimensional materials, especially rhombohedral boron monosulfide (r-BS), with its unique layered crystal structure, are being extensively studied for their potential applications in nanoelectronics. However, the analysis of the fundamental electronic properties of r-BS has been limited due to the lack of available large crystals. In this study, we utilize microfocused angle-resolved photoemission spectroscopy (micro-ARPES) to directly map the band structure of a tiny r-BS powder crystal, revealing that r-BS is a p-type semiconductor with an anisotropic in-plane effective mass and a band gap larger than 0.5 eV. These findings demonstrate the high applicability of micro-ARPES for investigating small powder crystals and provide new insights into the unexplored electronic states of novel materials.
Article
Nanoscience & Nanotechnology
Tappei Kawakami, Katsuaki Sugawara, Hirofumi Oka, Kosuke Nakayama, Ken Yaegashi, Seigo Souma, Takashi Takahashi, Tomoteru Fukumura, Takafumi Sato
Summary: This study reports on the unusual charge-density wave (CDW) in monolayer 2D VS2, which is associated with higher-order Fermi-surface nesting. The CDW exhibits a stripe pattern with periodicity of root 21R10.9 degrees root 3R30 degrees and opens an energy gap on the entire Fermi surface. The results suggest the involvement of a higher-order nesting vector 2q, twice as large as the normal nesting vector q, which is supported by anomalies in the calculated phonon dispersion and electronic susceptibility.
NPJ 2D MATERIALS AND APPLICATIONS
(2023)
Article
Chemistry, Multidisciplinary
Yasuaki Saruta, Katsuaki Sugawara, Hirofumi Oka, Tappei Kawakami, Takemi Kato, Kosuke Nakayama, Seigo Souma, Takashi Takahashi, Tomoteru Fukumura, Takafumi Sato
Summary: The current key challenge in 2D materials is to achieve emergent quantum phenomena in hetero structures by controlling the moire potential created by the periodicity mismatch between adjacent layers. This study demonstrates that the unstable octahedral MoTe2 can be stabilized in a commensurate MoTe2/graphene hetero-bilayer due to the moire potential between the two layers, providing a fresh approach to realize novel 2D quantum phases.
Article
Materials Science, Multidisciplinary
Koki Yanagizawa, Katsuaki Sugawara, Tappei Kawakami, Ryuichi Ando, Ken Yaegashi, Kosuke Nakayama, Seigo Souma, Kiyohisa Tanaka, Miho Kitamura, Koji Horiba, Hiroshi Kumigashira, Takashi Takahashi, Takafumi Sato
Summary: This study shows that monolayer titanium ditelluride's charge-density wave (CDW) can be switched conveniently by carrier tuning. The CDW appears only under certain conditions when partial Fermi-surface nesting occurs.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Taiki Taguchi, Katsuaki Sugawara, Hirofumi Oka, Tappei Kawakami, Yasuaki Saruta, Takemi Kato, Kosuke Nakayama, Seigo Souma, Takashi Takahashi, Tomoteru Fukumura, Takafumi Sato
Summary: We discovered that monolayer 1T-NbTe2 is a new class of two-dimensional transition-metal dichalcogenide (TMD) with a star-of-David lattice similar to bulk TaS2 and isostructural monolayer NbSe2. It exhibits a metallic ground state characterized by the sparsely occupied star-of-David lattice with a lattice periodicity of (19x19). By using various techniques, we found that the hidden Fermi-surface nesting and associated CDW formation are the primary causes for this unique correlated metallic state without a Mott gap.
Review
Multidisciplinary Sciences
Hongyun Zhang, Tommaso Pincelli, Chris Jozwiak, Takeshi Kondo, Ralph Ernstorfer, Takafumi Sato, Shuyun Zhou
Summary: The translation introduces the importance of electronic structure in solid-state materials and the advancement of ARPES technique for observing and studying electronic structures.
NATURE REVIEWS METHODS PRIMERS
(2022)
Article
Materials Science, Multidisciplinary
Takemi Kato, Yongkai Li, Kosuke Nakayama, Zhiwei Wang, Seigo Souma, Miho Kitamura, Koji Horiba, Hiroshi Kumigashira, Takashi Takahashi, Takafumi Sato
Summary: Polar surfaces and interfaces are crucial for realizing exotic properties of materials. In this study, the polar nature of the cleaved surface of CsV3Sb5 is investigated, revealing two different fermeological properties. Understanding the origin of unconventional superconducting and charge order at the surface of AV3Sb5 is highly dependent on these polar-surface-dependent band structures.
Article
Materials Science, Multidisciplinary
Takemi Kato, Yongkai Li, Tappei Kawakami, Min Liu, Kosuke Nakayama, Zhiwei Wang, Ayumi Moriya, Kiyohisa Tanaka, Takashi Takahashi, Yugui Yao, Takafumi Sato
Summary: In this study, the structural distortion responsible for the charge density wave in KV3Sb5 is investigated using angle-resolved photoemission spectroscopy and first-principles calculations, providing microscopic insight into the charge density wave and superconducting mechanisms.
COMMUNICATIONS MATERIALS
(2022)
