Editorial Material
Chemistry, Physical
Matthew Yankowitz
Summary: A new spectroscopic technique exploits overlapping electronic bands to investigate the highly correlated states of magic-angle twisted trilayer graphene.
Article
Multidisciplinary Sciences
Jeong Min Park, Yuan Cao, Kenji Watanabe, Takashi Taniguchi, Pablo Jarillo-Herrero
Summary: Moire superlattices have become a platform for studying correlated physics and superconductivity with unprecedented tunability. This study on magic-angle twisted trilayer graphene reveals a better tunability of electronic structure and superconducting properties than magic-angle twisted bilayer graphene, with implications for the understanding of strongly coupled superconductivity. The results suggest that the system can be electrically tuned close to the crossover to a two-dimensional Bose-Einstein condensate, indicating the potential for revolutionizing applications of superconductivity.
Article
Physics, Multidisciplinary
Xiaoxue Liu, Naiyuan James Zhang, K. Watanabe, T. Taniguchi, J. I. A. Li
Summary: The discovery of magic-angle twisted trilayer graphene and its integration into a double-layer structure provides important insights into the properties and stability of the superconducting phase. The findings also contribute to the development of theoretical models aiming to understand the nature of superconductivity.
Article
Chemistry, Multidisciplinary
Yiwei Li, Shihao Zhang, Fanqiang Chen, Liyang Wei, Zonglin Zhang, Hanbo Xiao, Han Gao, Moyu Chen, Shijun Liang, Ding Pei, Lixuan Xu, Kenji Watanabe, Takashi Taniguchi, Lexian Yang, Feng Miao, Jianpeng Liu, Bin Cheng, Meixiao Wang, Yulin Chen, Zhongkai Liu
Summary: Magic-angle twisted trilayer graphene (MATTG) has shown rich and unique properties, including superconductivity and distinct band structure. Experimental measurements reveal the coexistence of different bands in MATTG, which is crucial for further understanding its unconventional superconductivity.
ADVANCED MATERIALS
(2022)
Article
Multidisciplinary Sciences
Hyunjin Kim, Youngjoon Choi, Cyprian Lewandowski, Alex Thomson, Yiran Zhang, Robert Polski, Kenji Watanabe, Takashi Taniguchi, Jason Alicea, Stevan Nadj-Perge
Summary: Magic-angle twisted trilayer graphene (MATTG) is a moire material that exhibits strong electronic correlations and unconventional superconductivity. In this study, high-resolution scanning tunnelling microscopy and spectroscopy are used to investigate MATTG. Extensive regions of atomic reconstruction with mirror-symmetric stacking are observed, showing symmetry-breaking electronic transitions and doping-dependent band-structure deformations. Superconductivity is observed as pronounced dips in the tunnelling conductance at the Fermi level, accompanied by coherence peaks that become gradually suppressed at elevated temperatures and magnetic fields. The observed conductance evolution with doping suggests a transition from a gapped superconductor to a nodal superconductor, and the presence of peak-dip-hump structures indicates strong coupling to bosonic modes of MATTG.
Article
Materials Science, Multidisciplinary
Ammon Fischer, Zachary A. H. Goodwin, Arash A. Mostofi, Johannes Lischner, Dante M. Kennes, Lennart Klebl
Summary: Magic-angle twisted trilayer graphene is a highly tunable platform for studying correlated phases of matter. In this research, we find that spin fluctuations play an important role in superconductivity, and we discover new features in the phase diagram of the superconducting state.
NPJ QUANTUM MATERIALS
(2022)
Article
Physics, Multidisciplinary
Wei Qin, Allan H. MacDonald
Summary: Recent research has shown that superconductivity in magic-angle twisted trilayer graphene can survive in in-plane magnetic fields well beyond the Pauli limit, unlike magic-angle twisted bilayer graphene. The difference is attributed to the symmetry and relative displacements present in trilayers, which are not under experimental control at present. An gate electric field can break the symmetry and limit the in-plane critical magnetic field.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
Maine Christos, Subir Sachdev, Mathias S. Scheurer
Summary: Motivated by recent experiments in twisted-trilayer graphene, this study investigates the effects of interactions and superconductivity in this system close to the magic angle. The researchers identify ground states at different filling fractions and construct a phase diagram. They also study the superconducting properties of these states and find triplet pairing dominance in the experimentally relevant regime. The results have implications for future experiments and theoretical work in this field.
Article
Materials Science, Multidisciplinary
Xianqing Lin, Cheng Li, Kelu Su, Jun Ni
Summary: This study examines the energetic stability and local electronic structure of twisted trilayer graphene (TTG) with different twist angles. The results show that relaxed TTG supercells with specific twist angles can exhibit high density of states (DOS) near the Fermi level, while other stackings have lower DOS. Additionally, the local electronic structure of TTG can demonstrate strong spatial inhomogeneity depending on the stacking configuration.
Article
Multidisciplinary Sciences
Dorri Halbertal, Simon Turkel, Christopher J. Ciccarino, Jonas B. Hauck, Nathan Finney, Valerie Hsieh, Kenji Watanabe, Takashi Taniguchi, James Hone, Cory Dean, Prineha Narang, Abhay N. Pasupathy, Dante M. Kennes, D. N. Basov
Summary: The electronic and structural properties of atomically thin materials can be tuned by assembling them with an interlayer twist. In this study, the authors reveal surprising optical and electronic contrast in twisted double trilayer graphene and analyze the energetics of the unconventional lattice relaxation process. They demonstrate that this relaxation is non-local, leading to an energy gain in one domain of the moire lattice that is paid for by a relaxation in the other.
NATURE COMMUNICATIONS
(2022)
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
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
Materials Science, Multidisciplinary
Fang Xie, Nicolas Regnault, Dumitru Calugaru, B. Andrei Bernevig, Biao Lian
Summary: The study uses Hartree-Fock mean field approach to investigate the Hamiltonian of magic-angle twisted symmetric trilayer graphene, revealing different phases at different fillings and offering insights into the electron interactions in the system.
Article
Physics, Applied
Sanghyun Kim, Donghyeon Lee, Binbin Wang, Shang-Jie Yu, Kenji Watanabe, Takashi Taniguchi, Jonathan A. Fan, Jiamin Xue, Kayoung Lee
Summary: A Raman spectroscopic study of twisted artificial trilayer graphene (3LG) reveals distinctive 2D peak characteristics when the twist angle is greater than 5 degrees, and shows similarities to natural Bernal-stacked 3LG in non-twisted cases, indicating a thermodynamically stable state. Additionally, slightly twisted 3LG exhibits coexisting Bernal-stacked (ABA) and rhombohedral (ABC) domains.
APPLIED PHYSICS LETTERS
(2021)
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
Haidong Liang, Yuan Chen, Chengyuan Yang, Kenji Watanabe, Takashi Taniguchi, Goki Eda, Andrew A. Bettiol
Summary: This study demonstrates the generation of spin defects with high PL intensity and ODMR contrast using high-energy helium ion beams, while maintaining a small linewidth, thereby achieving good sensitivity. By comparing different fluences of helium irradiations, an optimal fluence is determined that can create spin defects without damaging the overall crystal lattice structure. Furthermore, with a focused beam, such spin defects can be created deterministically with nanometer precision.
ADVANCED OPTICAL MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Lucca Kuehner, Luca Sortino, Benjamin Tilmann, Thomas Weber, Kenji Watanabe, Takashi Taniguchi, Stefan A. Maier, Andreas Tittl
Summary: All-dielectric optical metasurfaces with high-Q resonances throughout the visible spectrum have been achieved by leveraging symmetry-broken quasi bound states in the continuum (qBICs). These qBIC resonances effectively suppress radiation losses, allowing for the use of low-index van der Waals materials such as hexagonal boron nitride (hBN). The experimental results also demonstrated enhanced second-harmonic generation using the high-Q resonances.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Hailong Fu, Ke Huang, Kenji Watanabe, Takashi Taniguchi, Morteza Kayyalha, Jun Zhu
Summary: In this experiment, Fabry-Perot interferometers were constructed using a split-gate design and measurements of Aharonov-Bohm oscillations were presented. The velocity of the edge state was found to be approximately 6 x 10(4) m/s at filling factor nu = 2 and decreased with increasing filling factor. The dc bias and temperature dependence of the interference suggested electron-electron interaction induced decoherence mechanisms. These results pave the way for exploring fractional and non-Abelian braiding statistics in this promising device platform.
Article
Nanoscience & Nanotechnology
Gabriel R. Jaffe, Keenan J. Smith, Kenji Watanabe, Takashi Taniguchi, Max G. Lagally, Mark A. Eriksson, Victor W. Brar
Summary: We measure the cross-plane thermal conductivity of hBN flakes exfoliated from bulk crystals and find that submicrometer thick flakes exhibit high thermal conductivities exceeding previously reported bulk values by more than 60%. We also find that introducing planar twist interfaces limits the maximum phonon mean free paths and decreases the cross-plane thermal conductivity of the stack.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Chemistry, Multidisciplinary
Yuan Chen, Haidong Liang, Leyi Loh, Yiwei Ho, Ivan Verzhbitskiy, Kenji Watanabe, Takashi Taniguchi, Michel Bosman, Andrew A. Bettiol, Goki Eda
Summary: We observe bound exciton (BX) complex manifolds in monolayer MoSe2 with intentionally created monoselenium vacancies (VSe) using proton beam irradiation. The emission intensity of different BX peaks exhibits contrasting dependence on electrostatic doping near the onset of free electron injection. These complexes, which are more strongly bound than trions and biexcitons, survive up to around 180 K and show moderate valley polarization memory, indicating partial free exciton character.
Article
Multidisciplinary Sciences
Haidong Tian, Xueshi Gao, Yuxin Zhang, Shi Che, Tianyi Xu, Patrick Cheung, Kenji Watanabe, Takashi Taniguchi, Mohit Randeria, Fan Zhang, Chun Ning Lau, Marc W. Bockrath
Summary: In a flat band superconductor, the charge carriers' velocity is extremely slow, leading to peculiar superconducting behavior. Using twisted bilayer graphene, the researchers investigate the effect of the slow velocity on the superconducting state. They find evidence for small Cooper pairs and discuss the unusual nature of ultra-strong coupling superconductivity in ultra-flat Dirac bands.
Article
Nanoscience & Nanotechnology
Yinong Zhang, Chengxin Xiao, Dmitry Ovchinnikov, Jiayi Zhu, Xi Wang, Takashi Taniguchi, Kenji Watanabe, Jiaqiang Yan, Wang Yao, Xiaodong Xu
Summary: Monolayer semiconducting transition metal dichalcogenides possess broken inversion symmetry and strong spin-orbit coupling, resulting in a unique spin-valley locking effect. In stacked multilayers, this effect leads to the formation of a spin-valley locked superlattice structure. Dipolar excitons, which have the electron and hole constituents separated in an every-other-layer configuration, become optically bright through hybridization with intralayer excitons. The reflectance spectra further reveal the presence of excited state orbitals and fine spectroscopy structures, indicating a sizable binding energy.
NATURE NANOTECHNOLOGY
(2023)
Article
Chemistry, Multidisciplinary
Danis I. Badrtdinov, Carlos Rodriguez-Fernandez, Magdalena Grzeszczyk, Zhizhan Qiu, Kristina Vaklinova, Pengru Huang, Alexander Hampel, Kenji Watanabe, Takashi Taniguchi, Lu Jiong, Marek Potemski, Cyrus E. Dreyer, Maciej Koperski, Malte Rosner
Summary: A key advantage of utilizing van-der-Waals (vdW) materials as defect-hosting platforms for quantum applications is the controllable proximity of the defect to the surface or the substrate, which allows for improved light extraction, enhanced coupling with photonic elements, or more sensitive metrology. However, this also poses a challenge for defect identification and characterization due to the influence of the atomic environment on the defect's properties. This study explores how the environment influences the properties of carbon impurity centers in hexagonal boron nitride (hBN) and demonstrates the dominant effect of the change in the environment on the screening of density-density Coulomb interactions between the defect orbitals.
Article
Chemistry, Multidisciplinary
Binghe Xie, Zijie Ji, Jiaxin Wu, Ruan Zhang, Yunmin Jin, Kenji Watanabe, Takashi Taniguchi, Zhao Liu, Xinghan Cai
Summary: Inelastic electron tunneling (IET) accompanied by energy transfer is widely used to study collective modes in solid-state materials. By directly observing IET in a graphene-based vertical tunnel junction device, characteristic features are linked to phonon-assisted IET, demonstrating a promising method for probing low-energy excitations in graphene-based van der Waals heterostructures.
Article
Chemistry, Multidisciplinary
Guorui Chen, Ya-Hui Zhang, Aaron Sharpe, Zuocheng Zhang, Shaoxin Wang, Lili Jiang, Bosai Lyu, Hongyuan Li, Kenji Watanabe, Takashi Taniguchi, Zhiwen Shi, David Goldhaber-Gordon, Yuanbo Zhang, Feng Wang
Summary: We report the observation of magnetic field-stabilized Wigner crystal states in ABC-stacked trilayer graphene on boron nitride (ABC-TLG/hBN). Correlated insulating states emerge at multiple fractional and integer fillings under a magnetic field. These insulating states can be attributed to generalized Mott states for integer fillings and generalized Wigner crystal states for fractional fillings. The nu = 2 insulating state persists up to 30 T and can be described by a Mott-Hofstadter transition at a high magnetic field.
Article
Chemistry, Multidisciplinary
Nikita V. Tepliakov, Ruize Ma, Johannes Lischner, Efthimios Kaxiras, Arash A. Mostofi, Michele Pizzochero
Summary: In this study, it is predicted that the recently fabricated heterojunctions of zigzag nanoribbons embedded in two-dimensional hexagonal boron nitride exhibit half-semimetallic behavior, with opposite energy shifts of the states residing at the two edges while maintaining their intrinsic antiferromagnetic exchange coupling. These heterojunctions undergo an antiferromagnetic-to-ferrimagnetic phase transition upon doping, where the sign of the excess charge controls the spatial localization of the net magnetic moments. This research holds promise for the development of carbon-based spintronics.
Article
Chemistry, Physical
Kahyun Ko, Ayoung Yuk, Rebecca Engelke, Stephen Carr, Junhyung Kim, Daesung Park, Hoseok Heo, Hyun-Mi Kim, Seul-Gi Kim, Hyeongkeun Kim, Takashi Taniguchi, Kenji Watanabe, Hongkun Park, Efthimios Kaxiras, Sang Mo Yang, Philip Kim, Hyobin Yoo
Summary: Conventional antiferroelectric materials can transition to a ferroelectric phase under strong electric fields, while twisted stacks of van der Waals crystals form moire superlattices with polar domains and anti-aligned dipoles. In this moire domain antiferroelectric (MDAF) arrangement, the distribution of electric dipoles is different from that of two-dimensional ferroelectrics. Through operando transmission electron microscopy, it has been observed that the topological protection provided by the domain wall network prevents the MDAF-to-FE transition in twisted bilayer WSe2. However, decreasing the twist angle leads to the disappearance of the domain wall network and the occurrence of this transition. Additionally, the analysis of pinning disorders provides insights on improving the switching speed of van der Waals ferroelectrics.
Article
Multidisciplinary Sciences
Zhen Lian, Dongxue Chen, Yuze Meng, Xiaotong Chen, Ying Su, Rounak Banerjee, Takashi Taniguchi, Kenji Watanabe, Sefaattin Tongay, Chuanwei Zhang, Yong-Tao Cui, Su-Fei Shi
Summary: By applying an electric field, the authors are able to manipulate the superposition between two moire sites in the trilayer WSe2 and monolayer WS2 system through hybridization with intralayer excitons. Moire superlattices of semiconducting transition metal dichalcogenides allow for unprecedented control of electron wavefunctions, leading to the emergence of quantum states.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Clarisse Fournier, Kenji Watanabe, Takashi Taniguchi, Julien Barjon, Stephanie Buil, Jean-Pierre Hermier, Aymeric Delteil
Summary: The ability to identify and characterize homogeneous and inhomogeneous dephasing processes is crucial in solid-state quantum optics. A combination of resonant laser excitation and second-order photon correlations allows access to fast dynamics. The color center in hexagonal boron nitride experiences spectral diffusion at a characteristic time scale of tens of microseconds while emitting Fourier-limited single photons between spectral jumps.
Article
Chemistry, Multidisciplinary
Caique Serati de Brito, Paulo E. Faria Junior, Talieh S. Ghiasi, Josep Ingla-Aynes, Cesar Ricardo Rabahi, Camila Cavalini, Florian Dirnberger, Samuel Manas-Valero, Kenji Watanabe, Takashi Taniguchi, Klaus Zollner, Jaroslav Fabian, Christian Schueller, Herre S. J. van der Zant, Yara Galvao Gobato
Summary: This study presents magneto photoluminescence investigations of monolayer MoSe2 on layered A-type antiferromagnetic semiconductor CrSBr. The results reveal a clear influence of CrSBr magnetic order on the optical properties of MoSe2, including anomalous linear-polarization dependence, changes of exciton/trion energies, magnetic-field dependence of PL intensities, and asymmetric magnetic proximity interaction in the valley g-factor. First-principles calculations suggest a broken-gap (type-III) band alignment in MoSe2/CrSBr, facilitating charge transfer processes. This work establishes the potential of antiferromagnetic-nonmagnetic interfaces in controlling the valley and excitonic properties of TMDs, with implications for opto-spintronics device development.
