Article
Physics, Multidisciplinary
Chun-Chih Tseng, Xuetao Ma, Zhaoyu Liu, Kenji Watanabe, Takashi Taniguchi, Jiun-Haw Chu, Matthew Yankowitz
Summary: This study reports the observation of the anomalous Hall effect in tBLG devices with twist angles slightly away from the magic angle, when both the electron and hole moire bands are at half filling. The findings suggest the existence of a stable valley-polarized ground state at half filling and highlight the need for a more complete understanding of the competing symmetry-breaking orders.
Article
Materials Science, Multidisciplinary
Jingtian Shi, Jihang Zhu, A. H. MacDonald
Summary: The quantum anomalous Hall (QAH) effect is sometimes observed in twisted bilayer graphene (tBG) when nearly aligned with an encapsulating hexagonal boron nitride (hBN) layer. The presence or absence of the QAH effect in individual devices is related to the commensurability between graphene/graphene and graphene/hBN moire patterns. The QAH effect is likely to occur when the moire patterns form a supermoire pattern near a commensurate point and have a percolating topologically nontrivial QAH phase.
Article
Physics, Multidisciplinary
Junxi Duan, Yu Jian, Yang Gao, Huimin Peng, Jinrui Zhong, Qi Feng, Jinhai Mao, Yugui Yao
Summary: In the study, a giant second-order nonlinear Hall effect dominated by disorder-induced skew scattering was observed in twisted bilayer graphene. The magnitude and direction of the nonlinearity could be effectively tuned by gate voltage, and was mainly determined by the collaboration of static and dynamic disorders.
PHYSICAL REVIEW LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Phanibhusan S. Mahapatra, Manjari Garg, Bhaskar Ghawri, Aditya Jayaraman, Kenji Watanabe, Takashi Taniguchi, Arindam Ghosh, U. Chandni
Summary: By utilizing marginally twisted bilayer graphene, a new type of Quantum Hall interferometer was demonstrated, showing distinct electronic Fabry-Perot and Aharonov-Bohm oscillations. Research findings suggest that interference effects are intrinsic to specific domains in the bilayer graphene, indicating diminished Coulomb charging effects.
Article
Physics, Multidisciplinary
Yves H. Kwan, Yichen Hu, Steven H. Simon, S. A. Parameswaran
Summary: The study reveals the topological features of neutral particle-hole pair excitations and their impact on the bound states in correlated QAH insulators. This results in the formation of topological exciton bands with robust features. The research also applies these ideas to broken-symmetry spontaneous QAH insulators in magic-angle twisted bilayer graphene with substrate alignment.
PHYSICAL REVIEW LETTERS
(2021)
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
Materials Science, Multidisciplinary
Cheng-Ping Zhang, Jiewen Xiao, Benjamin T. Zhou, Jin-Xin Hu, Ying-Ming Xie, Binghai Yan, K. T. Law
Summary: Recent studies have shown that moiré flat bands in twisted bilayer graphene (TBG) can exhibit nontrivial Berry curvatures when aligned with a hexagonal boron nitride substrate, resulting in a correlated Chern insulator near the 3/4 filling. This letter demonstrates that the large Berry curvatures in the moiré bands can induce a strong nonlinear Hall (NLH) effect in strained TBG. The giant NLH effect appears generically for a twist angle near the magic angle due to the strong susceptibility of nearly flat moiré bands to symmetry breaking induced by strains.
Article
Materials Science, Multidisciplinary
Jianpeng Liu, Xi Dai
Summary: Using an all-band Hartree-Fock variational method, the mechanisms behind correlated insulating states and quantum anomalous Hall effects in twisted bilayer graphene at integer fillings of flat bands have been explained. Correlated insulating states exhibit valley polarization and moire orbital antiferromagnetic ordering, while the quantum anomalous Hall states show spin and orbital ferromagnetic characteristics.
Article
Physics, Multidisciplinary
Hector Sainz-Cruz, Pierre A. Pantaleon, Vo Tien Phong, Alejandro Jimeno-Pozo, Francisco Guinea
Summary: Junctions between scanning tunneling microscope (STM) tip and superconducting twisted bilayer graphene (TBG) as well as TBG Josephson junctions (JJs) provide valuable insights into the symmetry of the superconductors' order parameter. Comparison of even and odd valley exchange superconducting phases (s-wave or f-wave) reveals that the critical current in mixed (s and f) JJs is strongly affected by the junction-lattice angle. Andreev reflection in STM-TBG junctions leads to a prominent subgap conductance peak in the case of f-wave, as observed in experiments.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Atasi Chakraborty, Kamal Das, Subhajit Sinha, Pratap Chandra Adak, Mandar M. Deshmukh, Amit Agarwal
Summary: Researchers investigated the family of second-order nonlinear anomalous (NLA) Hall effects in the moire system of twisted double bilayer graphene (TDBG), demonstrating that these effects can probe topological phase transitions. The study found that the entire family of NLA Hall responses undergo a sign reversal across a topological phase transition, establishing a deeper connection between valley topology and nonlinear Hall effects in time-reversal symmetric systems.
Article
Multidisciplinary Sciences
Yu Saito, Fangyuan Yang, Jingyuan Ge, Xiaoxue Liu, Takashi Taniguchi, Kenji Watanabe, J. I. A. Li, Erez Berg, Andrea F. Young
Summary: The study explores the finite-temperature dynamics of spin and valley isospins in magic-angle twisted bilayer graphene, revealing a resistivity peak at high temperatures near a superlattice filling factor of -1, suggesting a Pomeranchuk-type mechanism. The data indicate the presence of a finite-field magnetic phase transition and a small isospin stiffness in the system.
Article
Multidisciplinary Sciences
Meizhen Huang, Zefei Wu, Jinxin Hu, Xiangbin Cai, En Li, Liheng An, Xuemeng Feng, Ziqing Ye, Nian Lin, Kam Tuen Law, Ning Wang
Summary: This study reports a significant breakthrough in the efficiency of nonlinear Hall generation in small-angle-twisted bilayer WSe2, reaching 1000 V-1, which is a hundred times higher than the previous records. The researchers explained this result through the correlation-induced continuous Mott transition effect.
NATIONAL SCIENCE REVIEW
(2023)
Article
Optics
Zefeng Chen, Hongwei Yang, Yihong Xiao, Jintao Pan, Yu Xia, Wenguo Zhu
Summary: By calculating the optical conductivities of twisted bilayer graphene and studying the light-matter interaction, we investigated the photonic spin Hall effect in this material. Placing the graphene on a substrate and launching a Gaussian beam near the Brewster angle enhanced the effect, revealing the spin splitting and Goos-Hanchen shifts associated with the surface conductivities. These findings deepen our understanding and indicate potential applications in characterizing bilayer graphene.
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION
(2021)
Article
Physics, Multidisciplinary
Petr Stepanov, Ming Xie, Takashi Taniguchi, Kenji Watanabe, Xiaobo Lu, Allan H. MacDonald, B. Andrei Bernevig, Dmitri K. Efetov
Summary: Research has shown that the odd integer filling factors in h-BN nonaligned devices correspond to symmetry broken Chern insulators with a Chern number of C = +1 and a relatively high Curie temperature. Under a perpendicular magnetic field, the Chern insulator at v = +1 transitions from C = +1 to C = 3, characterized by a quantized Hall plateau. Additionally, the device exhibits strong superconducting phases with critical temperatures up to Tc ≈ 3.5 K.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
Meizhen Huang, Zefei Wu, Xu Zhang, Xuemeng Feng, Zishu Zhou, Shi Wang, Yong Chen, Chun Cheng, Kai Sun, Zi Yang Meng, Ning Wang
Summary: The observation of the quantum anomalous Hall effect and nonlocal transport response in twisted bilayer graphene reveals the existence of nontrivial band topology governed by Berry curvature. However, recent works have shown that nonlinear Hall signals in graphene superlattices are caused by extrinsic disorder scattering instead of intrinsic Berry curvature dipole moment. In this study, we report an intrinsic nonlinear Hall effect induced by Berry curvature dipole in high-quality twisted bilayer graphene devices. We also demonstrate that the application of the displacement field can significantly change the direction and amplitude of the nonlinear Hall voltages through a field-induced sliding of the Berry curvature hotspots. Our findings not only establish the dominant role of Berry curvature dipole in generating intrinsic nonlinear Hall signals in graphene superlattices with low disorder densities, but also highlight the potential of twisted bilayer graphene as a sensitive and fine-tunable platform for second harmonic generation and rectification.
PHYSICAL REVIEW LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Fuqing Yu, Haonan Zhao, Yingzhong Li, Guomin Xia, Hongming Wang
Summary: This study demonstrates the synthesis and investigation of organic D-A-type fluorophores, Np-TPA and Np-2TPA, with strong fluorescence emission in both dilute solutions and the solid state. The conformation planarization in the excited state allows for intense emission in solution, while highly restricted pi-pi stacking permits bright emission in the crystalline state. These results suggest that dual-state emissive fluorophores represent a new paradigm for bioimaging.
MATERIALS CHEMISTRY FRONTIERS
(2022)
Article
Chemistry, Multidisciplinary
Yigang Wang, Guomin Xia, Manman Tan, Mingda Wang, Yingzhong Li, Hongming Wang
Summary: Understanding and implementing ordered supramolecular assembly in organic photothermal materials is challenging but significant. In this study, an amphipathic squaraine dye (PSQ) with a poly (ethylene glycol) chain attached was synthesized and self-assembled into nanospheres with well-defined H-dimeric substructures. Molecular dynamics simulations were conducted to illustrate the self-assembly process. The resulting H-dimeric nanospheres showed ultrahigh photothermal conversion efficiency and exhibited good stability, biocompatibility, tumor accumulation, and efficient tumor inhibition in photothermal therapy. These findings provide a unique platform for the precise design of small-molecule photothermal agents for future clinical applications of photothermal therapy.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Chemistry, Inorganic & Nuclear
Caiju Jin, Zijuan Chen, Shunli Shi, Ying Li, Sanmei Liu, Shuhua Wang, Hongming Wang, Chao Chen
Summary: In this study, chiral metal-organic frameworks (CMOFs) with a hierarchical micro/ mesoporous structure were synthesized using a mechanochemical process. The construction strategy was simple, green, and rapid, allowing for the solvent-free production of gram-scale CMOFs. The as-synthesized CMOFs showed excellent catalytic performance in Aldol asymmetric catalysis.
INORGANIC CHEMISTRY
(2022)
Article
Chemistry, Physical
Caiju Jin, Shunli Shi, Sheng Liao, Sanmei Liu, Siyao Xia, Yanping Luo, Shuhua Wang, Hongming Wang, Chao Chen
Summary: We report a rapid synthesis of functionalized metal-organic frameworks (MOFs) by integrating post-synthetic ligand exchange (PSLE) and mechanochemistry. This mechano-PSLE approach overcomes the challenges of PSLE, such as long reaction time, excessive solvent, and PSLE failure under solvothermal conditions. The gram-scale MOF functionalized with a chiral group can be obtained easily and in an environmentally friendly manner. It exhibits excellent asymmetric catalytic performance, providing a basis for the industrial production of functionalized MOFs.
CHEMISTRY OF MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Fuqing Yu, Xian Liu, Luliang Liao, Guomin Xia, Hongming Wang
Summary: Electrochemical CO2 reduction reaction (CO2RR) is an effective approach to address CO2 emission and synthesize high-value multi-carbon (C2+) chemicals. Constructing multilayer-bound nanoreactors is a promising strategy to manage intermediate CO and produce C2+ products. In this study, Ag@Cu2O nanoreactors were designed and optimized, demonstrating high Faradaic efficiency and stability during C2+ production. The study also provides insights into CO retention and ethanol generation in multilayer-bound nanoreactors.
Article
Chemistry, Multidisciplinary
G. Xia, L. Si, H. Wang
Summary: Dual-state emission refers to the phenomenon where organic molecules exhibit bright emission in both dilute solution and solid states. This concept has contributed to the understanding of photophysical areas and practical applications of mono-state emission. This review focuses on the structural features and working principles of dual-state emissive luminogens (DSEgens), highlighting the importance of intramolecular p-conjugated rigidity and twisted conformation in their efficient construction. The correlation between molecular configurations and emission properties of DSEgens is analyzed, with a focus on emission efficiency and wavelength variability. Preliminary applications and future perspectives of DSEgens are also discussed.
MATERIALS TODAY CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Xianshi Zeng, Luliang Liao, Qiming Yu, Meishan Wang, Hongming Wang
Summary: This study investigates metal-organic frameworks (MOFs) composed of transition metals and organic ligands as potential electrocatalysts for CO2 reduction. Through testing ten different catalysts, this study finds that seven of them exhibit high CO2 reduction selectivity.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Article
Chemistry, Physical
Xianshi Zeng, Luliang Liao, Meishan Wang, Hongming Wang
Summary: Metal-organic frameworks (MOFs) have excellent performance in electrocatalytic reduction of CO2 and can address resource scarcity and climate issues. The two-dimensional MOF constructed from transition metal-hexaiminotriphenylene was found to be an ideal electrocatalyst based on theoretical calculations and reliable data. Various metal catalysts showed promising catalytic activity and can be used for CO2 reduction.
CATALYSIS SCIENCE & TECHNOLOGY
(2023)
Article
Chemistry, Multidisciplinary
Weihan Guo, Mingda Wang, Leilei Si, Yigang Wang, Guomin Xia, Hongming Wang
Summary: We designed a propeller-like squaraine dye SQ-NMe2 decorated with four peripheral dimethylamines to achieve high sensitivity and wide-range color switching in piezochromic fluorescent materials. The precise peripheral design improves molecular packing and facilitates intramolecular charge transfer under mechanical stimuli. The SQ-NMe2 microcrystals exhibit significant fluorescence changes from yellow to orange to deep red, making them suitable for crytographic applications.
Article
Chemistry, Multidisciplinary
Yigang Wang, Mingda Wang, Guomin Xia, Yang Yang, Leilei Si, Hua Wang, Hongming Wang
Summary: The first acceptor-substituted squaraine fluorophore with a maximum emission wavelength beyond 1200 nm has been developed, exhibiting ultra-high brightness and photostability. It can co-assemble with bovine serum albumin to form a biocompatible dye-protein nanocomplex, leading to significant fluorescence enhancement for high-resolution vascular imaging.
CHEMICAL COMMUNICATIONS
(2023)
Article
Chemistry, Physical
Liming Hong, Xian Liu, Baozhu Chi, Guomin Xia, Hongming Wang
Summary: This study successfully designed and prepared a precise diatomic catalyst that achieves synergistic adsorption and activation of H2O and CO2 molecules through strong hydrogen bonding, thereby improving the efficiency and product selectivity of CO2 electroreduction.
JOURNAL OF MATERIALS CHEMISTRY A
(2023)
Article
Materials Science, Biomaterials
Yingzhong Li, Lizhen Chen, Leilei Si, Yang Yang, Chunlei Zhou, Fuqing Yu, Guomin Xia, Hongming Wang
Summary: By utilizing triphenylamine-equipped 1,8-naphthaolactam (NP-TPA) as a versatile scaffold, an efficient subcellular imaging agent (NP-TPA-Tar) was designed with bright and constant emissions, significant Stokes shifts, and easy modifiability. The NP-TPA-Tar can efficiently map the spatial distribution of lysosomes, mitochondria, endoplasmic reticulum, and plasma membrane in Hep G2 cells. Compared to its commercial counterpart, NP-TPA-Tar exhibits increased Stokes shift, enhanced photostability, improved targeting capability, and comparable imaging efficiency even at low concentrations (50 nM). This work will advance the development of imaging agents and improve super-resolution and real-time imaging in biological applications.
JOURNAL OF MATERIALS CHEMISTRY B
(2023)
Article
Chemistry, Organic
Wei Chen, Jingjun Fang, Jian Huang, Qin Yang, Zhibin Song, Qiuping Ding, Hongming Wang, Yiyuan Peng
Summary: An efficient method for direct regioselective acylation of quinazolines under metal-free conditions was developed. The reaction showed good to excellent yields, excellent functional group tolerance and site selectivity. The mechanism of the reaction was investigated using multiple analytical strategies.
ORGANIC & BIOMOLECULAR CHEMISTRY
(2023)
Article
Chemistry, Physical
Xian Liu, Luliang Liao, Guomin Xia, Fuqing Yu, Guangyao Zhang, Minxing Shu, Hongming Wang
Summary: This study proposes a new strategy to maintain both the precise Ni-N2C2 structure and high metal loading by using a Ni-salen polymer precursor with a confined metal position and precise coordination mode. The resulting Ni-N2C2 SAC exhibits excellent catalytic performance in the electroreduction of CO2 to CO.
JOURNAL OF MATERIALS CHEMISTRY A
(2022)
