Article
Multidisciplinary Sciences
Yonglong Xie, Andrew T. Pierce, Jeong Min Park, Daniel E. Parker, Eslam Khalaf, Patrick Ledwith, Yuan Cao, Seung Hwan Lee, Shaowen Chen, Patrick R. Forrester, Kenji Watanabe, Takashi Taniguchi, Ashvin Vishwanath, Pablo Jarillo-Herrero, Amir Yacoby
Summary: Fractional Chern insulators (FCIs) are lattice analogues of fractional quantum Hall states and have been recently observed in magic-angle twisted BLG at low magnetic field. The appearance of these states at 5 T is accompanied by the disappearance of nearby topologically trivial charge density wave states.
Article
Multidisciplinary Sciences
Youngjoon Choi, Hyunjin Kim, Yang Peng, Alex Thomson, Cyprian Lewandowski, Robert Polski, Yiran Zhang, Harpreet Singh Arora, Kenji Watanabe, Takashi Taniguchi, Jason Alicea, Stevan Nadj-Perge
Summary: Magic-angle twisted bilayer graphene (MATBG) exhibits a variety of correlated phenomena, and new techniques introduced can determine the topological phases that emerge in MATBG in a finite magnetic field. These topological phases form only in a specific range of twist angles and are influenced by strong electronic interactions.
Article
Materials Science, Multidisciplinary
Yajuan Cheng, Zheyong Fan, Tao Zhang, Masahiro Nomura, Sebastian Volz, Guimei Zhu, Baowen Li, Shiyun Xiong
Summary: We report a local minimum in thermal conductivity in twisted bilayer graphene (TBG) at the angle of 1.08 degrees, which corresponds to the 'magic angle' in the transition of several other reported properties. The thermal magic angle arises from the competition between the delocalization of atomic vibrational amplitudes and stresses on one hand, and the increased AA stacking density on the other hand. The manifestation of a magic angle, disclosing new thermal mechanisms at nanoscale, further uncovers the unique physics of two-dimensional materials.
MATERIALS TODAY PHYSICS
(2023)
Article
Multidisciplinary Sciences
J. Diez-Merida, A. Diez-Carlon, S. Y. Yang, Y. -M. Xie, X. -J. Gao, J. Senior, K. Watanabe, T. Taniguchi, X. Lu, A. P. Higginbotham, K. T. Law, Dmitri K. Efetov
Summary: The authors demonstrate a Josephson junction in magic-angle twisted bilayer graphene with a correlated insulator weak link, showing magnetism and programmable superconducting diode behavior. The coexistence of gate-tunable superconducting, magnetic and topological orders in magic-angle twisted bilayer graphene provides opportunities for the creation of hybrid Josephson junctions.
NATURE COMMUNICATIONS
(2023)
Article
Multidisciplinary Sciences
Xiaoxue Liu, Zhi Wang, K. Watanabe, T. Taniguchi, Oskar Vafek, J. I. A. Li
Summary: This study introduces a new device geometry to continuously tune the strength of electron-electron Coulomb interaction within twisted bilayer graphene, revealing opposite effects of charge screening on insulating and superconducting states.
Article
Chemistry, Multidisciplinary
Giorgio Di Battista, Paul Seifert, Kenji Watanabe, Takashi Taniguchi, Kin Chung Fong, Alessandro Principi, Dmitri K. Efetov
Summary: In this study, the thermal properties of superconducting MATBG were revealed by monitoring its temperature dependent critical current. The temperature dependence of the electronic thermal conductance was extracted, laying the foundation for future thermal transport studies on this system.
Article
Physics, Condensed Matter
Thi-Nga Do, Po-Hsin Shih, Godfrey Gumbs
Summary: The magic-angle twisted bilayer graphene (MATBLG) with special flat bands exhibits exotic physical properties, but exploiting the engineering of these properties by external fields is still in its early stages. We show that MATBLG under an external magnetic field presents a distinctive magnetoplasmon dispersion, which can be significantly modified by transferred momentum and charge doping. Special pronounced single magnetoplasmon and horizontal single-particle excitation modes near charge neutrality exist along a wide range of transferred momentum. We provide an insightful discussion of these unique features based on the electronic excitation of Landau levels quantized from the flat bands and Landau damping. Additionally, charge doping leads to peculiar multiple strong-weight magnetoplasmons. These characteristics make MATBLG a favorable candidate for plasmonic devices and technology applications.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2023)
Article
Chemistry, Multidisciplinary
Xiaoqian Liu, Ran Peng, Zhaoru Sun, Jianpeng Liu
Summary: In this study, the phonon properties of magic-angle twisted bilayer graphene (TBG) were investigated using many-body classical potential and interatomic forces generated by a deep neural network. Various vibrational patterns and their effects on electronic structures were discovered.
Article
Chemistry, Physical
Nathanael P. Kazmierczak, Madeline Van Winkle, Colin Ophus, Karen C. Bustillo, Stephen Carr, Hamish G. Brown, Jim Ciston, Takashi Taniguchi, Kenji Watanabe, D. Kwabena Bediako
Summary: Twisted bilayer graphene exhibits two-regime reconstruction mechanics based on twist angle, with applied heterostrain accumulating anisotropically in saddle-point regions to generate distinctive striped strain phases. Nanoscale spatial fluctuations in twist angle and uniaxial heterostrain were statistically evaluated, revealing the prevalence of short-range disorder in moire heterostructures. This study provides insights into the twist-angle-dependent electronic behavior and structural relaxation, disorder, and strain in moire materials.
Article
Materials Science, Multidisciplinary
Tiago C. Barbosa, Andreij C. Gadelha, Douglas A. A. Ohlberg, Kenji Watanabe, Takashi Taniguchi, Gilberto Medeiros-Ribeiro, Ado Jorio, Leonardo C. Campos
Summary: In this study, we investigated the Raman spectra of twisted bilayer graphene samples with different twist angles. The results showed that electron-phonon interaction affects the linewidth of the G band, particularly near the magic angle. The lineshape of the 2D band is determined by the crystal lattice and strain soliton regions.
Article
Physics, Multidisciplinary
Pawel Potasz, Ming Xie, A. H. MacDonald
Summary: This study reports on finite-size exact-diagonalization calculations in a Hilbert space defined by the continuum-model flat moire bands of magic angle twisted bilayer graphene, showing evidence of a spin ferromagnet ground state for moire band filling between 3 and 2, and Chern insulator ground states with spontaneous spin, valley, and sublattice polarization near filling 3. It is emphasized that the inclusion of remote band self-energy is crucial for a reliable description of flat band correlations in magic angle twisted bilayer graphene.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
Simone Lisi, Xiaobo Lu, Tjerk Benschop, Tobias A. de Jong, Petr Stepanov, Jose R. Duran, Florian Margot, Irene Cucchi, Edoardo Cappelli, Andrew Hunter, Anna Tamai, Viktor Kandyba, Alessio Giampietri, Alexei Barinov, Johannes Jobst, Vincent Stalman, Maarten Leeuwenhoek, Kenji Watanabe, Takashi Taniguchi, Louk Rademaker, Sense Jan van der Molen, Milan P. Allan, Dmitri K. Efetov, Felix Baumberger
Summary: Research utilizing nano-ARPES on twisted bilayer graphene directly shows the presence of flat bands and key features in the band structure.
Article
Physics, Multidisciplinary
Yang-Zhi Chou, Sankar Das Sarma
Summary: In this study, we systematically investigate emergent Kondo lattice models in magic-angle twisted bilayer graphene using the topological heavy fermion representation. We demonstrate a series of symmetric strongly correlated metallic states and possibly realize a topological Dirac Kondo semimetal. The findings suggest that magic-angle twisted bilayer graphene may serve as a solid-state quantum simulator for novel magnetic orders on a triangular lattice.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
Alexandre Jaoui, Ipsita Das, Giorgio Di Battista, Jaime Diez-Merida, Xiaobo Lu, Kenji Watanabe, Takashi Taniguchi, Hiroaki Ishizuka, Leonid Levitov, Dmitri K. Efetov
Summary: This study presents transport measurements in superconducting MATBG, where the correlated insulator states are suppressed by screening. The uninterrupted metallic ground state exhibits linear resistivity and Planckian scattering rates. A quantum-critical phase dominates the metallic ground state in a continuum of doping.
Article
Physics, Multidisciplinary
Alexina Ollier, Marcin Kisiel, Xiaobo Lu, Urs Gysin, Martino Poggio, Dmitri K. Efetov, Ernst Meyer
Summary: This study investigates the low-temperature nanomechanical energy dissipation of twisted bilayer graphene using pendulum atomic force microscopy. The authors observe different doping regions and wavefunction interference between these regions.
COMMUNICATIONS PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Yejin Lee, Mickey Martini, Tommaso Confalone, Sanaz Shokri, Christian N. Saggau, Daniel Wolf, Genda Gu, Kenji Watanabe, Takashi Taniguchi, Domenico Montemurro, Valerii M. Vinokur, Kornelius Nielsch, Nicola Poccia
Summary: A new method of fabricating twisted van der Waals heterostructures can improve the performance of Josephson junctions in high-temperature cuprate superconductors, making them comparable to intrinsic junctions in bulk samples. The method combines cryogenic stacking and covering the interface with insulating hexagonal boron nitride crystals. The study also shows that encapsulated interfaces are more stable than unencapsulated ones.
ADVANCED MATERIALS
(2023)
Article
Physics, Applied
Shingo Genchi, Shu Nakaharai, Takuya Iwasaki, Kenji Watanabe, Takashi Taniguchi, Yutaka Wakayama, Azusa N. N. Hattori, Hidekazu Tanaka
Summary: Vanadium dioxide (VO2) shows an insulator-metal transition (IMT) and a significant resistance change, which is attractive for device applications like switching. The behavior of individual domains determines the overall IMT property of the VO2 sample, allowing the identification and utilization of steep resistance changes from single domains. Unique step resistance changes are observed in micro-structured VO2 thin films on hexagonal boron nitride (hBN) due to the confined metallic domains. This study demonstrated step electrical switching in a two-terminal VO2 sample on hBN and revealed how the emergence of metallic domains in the micrometer space contributes to the increase in electric current.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Xiaohui Xu, Abhishek B. Solanki, Demid Sychev, Xingyu Gao, Samuel Peana, Aleksandr S. Baburin, Karthik Pagadala, Zachariah O. Martin, Sarah N. Chowdhury, Yong P. Chen, Takashi Taniguchi, Kenji Watanabe, Ilya A. Rodionov, Alexander Kildishev, Tongcang Li, Pramey Upadhyaya, Alexandra Boltasseva, Vladimir M. Shalaev
Summary: The negatively charged boron vacancy defect in boron nitride has potential in quantum sensing, but its low quantum efficiency hampers its practical applications. This study demonstrates significantly higher emission enhancements of the defect using low-loss nanopatch antennas, making it a promising high-resolution magnetic field sensor.
Article
Chemistry, Multidisciplinary
Hugh Ramsden, Soumya Sarkar, Yan Wang, Yiru Zhu, James Kerfoot, Evgeny M. Alexeev, Takashi Taniguchi, Kenji Watanabe, Sefaattin Tongay, Andrea C. Ferrari, Manish Chhowalla
Summary: van der Waals heterostructures (vdW-HSs) integrate dissimilar materials to form complex devices, relying on the manipulation of charges at multiple interfaces. Conductive mode and cathodoluminescence scanning electron microscopy (CM-SEM and SEM-CL) were used to investigate the trapping of charges in vdW-HSs during electron irradiation, which can adversely affect the performance of the devices. The results showed that up to 70% of beam electrons are deposited into the vdW-HS, leading to dynamic doping of 1L-WSe2 and reducing its cathodoluminescence efficiency. CM-SEM and SEM-CL provide a toolkit for nanoscale characterization of vdW-HS devices, allowing for the correlation of electrical and optical properties.
Article
Physics, Multidisciplinary
Siyu Li, Zhengwen Wang, Yucheng Xue, Lu Cao, Kenji Watanabe, Takashi Taniguchi, Hongjun Gao, Jinhai Mao
Summary: In this study, the distribution patterns of flat bands in twisted monolayer-bilayer graphene (tMBG) were observed using scanning tunneling microscopy and spectroscopy (STM/S), revealing two different modes of flat band distributions. By adjusting the electric field, the distribution of the two flat bands transitioned from a localized mode to a delocalized mode. This gate-controlled flat band wavefunction polarization is unique to the tMBG system, highlighting its potential in simulating twisted bilayer graphene (TBG) and twisted double bilayer graphene (tDBG), and exploring novel moire physics.
Article
Chemistry, Multidisciplinary
Zhijie Li, Farsane Tabataba-Vakili, Shen Zhao, Anna Rupp, Ismail Bilgin, Ziria Herdegen, Benjamin Maerz, Kenji Watanabe, Takashi Taniguchi, Gabriel Ravanhani Schleder, Anvar S. Baimuratov, Efthimios Kaxiras, Knut Mueller-Caspary, Alexander Hoegele
Summary: Vertical van der Waals heterostructures of semiconducting transition metal dichalcogenides synthesized by chemical vapor deposition exhibit atomic reconstruction, leading to the coexistence of moire-type cores and extended moire-free regions in heterostacks with parallel and antiparallel alignment. This work highlights the potential of chemical vapor deposition for applications requiring laterally extended heterosystems or exciton-confining heterostack arrays of one atomic registry.
Article
Multidisciplinary Sciences
Jiaqi Cai, Eric Anderson, Chong Wang, Xiaowei Zhang, Xiaoyu Liu, William Holtzmann, Yinong Zhang, Fengren Fan, Takashi Taniguchi, Kenji Watanabe, Ying Ran, Ting Cao, Liang Fu, Di Xiao, Wang Yao, Xiaodong Xu
Summary: This study reports experimental evidence of fractional quantum anomalous Hall (FQAH) states in twisted MoTe2 bilayers. By using magnetic circular dichroism measurements and trion photoluminescence as a sensor, the researchers demonstrate the presence of FQAH states by observing the corresponding dispersion curves and linear shifts. These topological states can be electrically driven into topologically trivial states and provide a platform for exploring fractional excitations.
Article
Physics, Multidisciplinary
Heonjoon Park, Jiayi Zhu, Xi Wang, Yingqi Wang, William Holtzmann, Takashi Taniguchi, Kenji Watanabe, Jiaqiang Yan, Liang Fu, Ting Cao, Di Xiao, Daniel R. Gamelin, Hongyi Yu, Wang Yao, Xiaodong Xu
Summary: Strong dipole-dipole interactions in a moire superlattice form a ground state similar to a Mott insulator, making it a powerful platform for engineering correlated electronic phenomena. Optical excitation generates charge neutral interlayer excitons with an out-of-plane electric dipole. Strong onsite dipole-dipole interaction can create correlated bosonic states, but this has not been proven yet.
Article
Materials Science, Multidisciplinary
Aleksander Rodek, Thilo Hahn, James Howarth, Takashi Taniguchi, Kenji Watanabe, Marek Potemski, Piotr Kossacki, Daniel Wigger, Jacek Kasprzak
Summary: In this study, we performed ultrafast coherent nonlinear spectroscopy of a charge-tunable MoSe2 monolayer. The experiments showed that the properties of exciton complexes, such as line width and population decay, can be directly tuned by an applied gate bias. Furthermore, we demonstrated that this bias-tuning approach can also control the coherent coupling strength between charged and neutral exciton complexes.
Article
Chemistry, Multidisciplinary
Soo Yeon Lim, Han-gyu Kim, Young Woo Choi, Takashi Taniguchi, Kenji Watanabe, Hyoung Joon Choi, Hyeonsik Cheong
Summary: We present a detailed analysis of the interlayer interaction dependent on the twist angle in WSe2/MoSe2 hetero-twisted bilayer (TBL) through Raman and photoluminescence studies combined with first-principles calculation. Different interlayer vibrational modes, moiré phonons, and interlayer excitonic states with distinct characteristics are observed and identified as the twist angle evolves. Moreover, the interlayer excitons in hetero-TBLs with twist angles near 0 degrees or 60 degrees exhibit different energies and photoluminescence excitation spectra due to variations in electronic structures and carrier relaxation dynamics. These findings contribute to a better understanding of the interlayer interaction in hetero-TBLs.
Article
Chemistry, Multidisciplinary
Daniel J. Rizzo, Jin Zhang, Bjarke S. Jessen, Francesco L. Ruta, Matthew Cothrine, Jiaqiang Yan, David G. Mandrus, Stephen E. Nagler, Takashi Taniguchi, Kenji Watanabe, Michael M. Fogler, Abhay N. Pasupathy, Andrew J. Millis, Angel Rubio, James C. Hone, Cory R. Dean, D. N. Basov
Summary: The use of work-function-mediated charge transfer is explored for nanoscale electrostatic control of atomic layers. A thin layer of a-RuCl3 is found to induce emergent nano-optical behavior in hBN through interlayer charge polarization. The propagation length of hBN phonon polaritons is significantly reduced by the interfacial dipole formed by a-RuCl3, and a novel resonance is observed in nano-optical spectroscopy experiments. These findings demonstrate the potential of charge-transfer heterostructures for tailoring optoelectronic properties of 2D insulators.
Article
Nanoscience & Nanotechnology
Zui Tao, Bowen Shen, Wenjin Zhao, Nai Chao Hu, Tingxin Li, Shengwei Jiang, Lizhong Li, Kenji Watanabe, Takashi Taniguchi, Allan H. MacDonald, Jie Shan, Kin Fai Mak
Summary: A giant intrinsic spin Hall effect coexisting with ferromagnetism has been observed in AB-stacked MoTe2/WSe2 moire hetero-bilayers. This finding demonstrates the potential of moire engineering for spintronics applications, as it enables long-range spin Hall transport.
NATURE NANOTECHNOLOGY
(2023)
Article
Multidisciplinary Sciences
Qing Rao, Wun-Hao Kang, Hongxia Xue, Ziqing Ye, Xuemeng Feng, Kenji Watanabe, Takashi Taniguchi, Ning Wang, Ming-Hao Liu, Dong-Keun Ki
Summary: Van der Waals interactions induce strong spin-orbit coupling in transition metal dichalcogenides, providing a promising way to combine the experimental flexibility of graphene with the tuning capabilities of spin-orbit coupling. By measuring ballistic transverse magnetic focusing in graphene on WSe2, SOC-driven band splitting and electron dynamics are studied. Possible suppression of electron-electron scatterings is observed and weak band splitting is found in Shubnikov-de Haas oscillations.
NATURE COMMUNICATIONS
(2023)
Article
Physics, Multidisciplinary
Wenhao Huang, Tathagata Paul, Kenji Watanabe, Takashi Taniguchi, Mickael L. Perrin, Michel Calame
Summary: In this study, the presence of viscous effects in high-mobility graphene field-effect transistors has been confirmed through investigations on the electronic characteristics of viscous charge flow. Design guidelines for devices with increased viscous effects have been provided based on finite element calculations. The existence of viscous effects opens up opportunities for the design of functional hydrodynamic devices such as geometric rectifiers and charge amplifiers based on the electronic Venturi effect.
PHYSICAL REVIEW RESEARCH
(2023)
Article
Chemistry, Multidisciplinary
Mehdi Arfaoui, Natalia Zawadzka, Sabrine Ayari, Zhaolong Chen, Kenji Watanabe, Takashi Taniguchi, Adam Babinski, Maciej Koperski, Sihem Jaziri, Maciej R. Molas
Summary: Investigated the optical properties of anisotropic excitons in GeS encapsulated by h-BN. Found that the exciton behavior is strongly influenced by the Coulomb interaction and exhibits polarization-dependent and anisotropic nature.