Article
Engineering, Mechanical
Tawfiqur Rakib, Pascal Pochet, Elif Ertekin, Harley T. Johnson
Summary: We observe a helical dislocation network accompanied by large out-of-plane deformation in twisted bilayer graphene (tBLG). By atomistic calculations, we demonstrate two distinct out-of-plane deformation modes, a breathing mode with small deformation and a bending mode with significantly larger corrugation. The out-of-plane deformation is caused by inhomogeneous interlayer coupling resulting from the periodic stacking order of the tBLG moire superlattice.
EXTREME MECHANICS LETTERS
(2023)
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
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
Multidisciplinary Sciences
Yuan Hou, Zhaohe Dai, Shuai Zhang, Shizhe Feng, Guorui Wang, Luqi Liu, Zhiping Xu, Qunyang Li, Zhong Zhang
Summary: This study demonstrates that nanopockets in vdW materials can coalesce spontaneously into larger spaces which can be easily cleaned through mechanical methods, and that bilayer graphene interfaces exhibit excellent self-renewal phenomena in terms of moire patterns recovery after motion of contaminants.
NATURE COMMUNICATIONS
(2021)
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
Materials Science, Multidisciplinary
Ipsita Mandal, Jia Yao, Erich J. Mueller
Summary: Experiments have shown that insulating behavior emerges in graphene bilayers when the moire bands are partially filled and the top layer is rotated relative to the bottom layer. By calculating charge distributions and estimating excitation gaps, researchers are able to further understand the properties of these phases.
Article
Physics, Multidisciplinary
Dumitru Calugaru, Nicolas Regnault, Myungchul Oh, Kevin P. Nuckolls, Dillon Wong, Ryan L. Lee, Ali Yazdani, Oskar Vafek, B. Andrei Bernevig
Summary: This article analytically computes the scanning tunneling microscopy (STM) signatures of integer-filled correlated ground states of the magic angle twisted bilayer graphene (TBG) narrow bands and assesses the possibility of Kekule distortion (KD). The results show that coupling the two opposite graphene valleys does not always result in KD.
PHYSICAL REVIEW LETTERS
(2022)
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
Materials Science, Multidisciplinary
Jiseon Shin, Bheema Lingam Chittari, Yunsu Jang, Hongki Min, Jeil Jung
Summary: In this study, we investigate the electronic structure of alternating-twist triple Bernal-stacked bilayer graphene (t3BG) by varying interlayer coupling, twist angle, interlayer potential difference, and sliding vector. We find that under certain parameters, the bands can flatten down to low energy levels, facilitating the formation of correlation-driven gaps.
Article
Multidisciplinary Sciences
Manabendra Kuiri, Christopher Coleman, Zhenxiang Gao, Aswin Vishnuradhan, Kenji Watanabe, Takashi Taniguchi, Jihang Zhu, Allan H. MacDonald, Joshua Folk
Summary: This study discovered a strong anomalous Hall effect in twisted double bilayer graphene, suggesting the breaking of time reversal symmetry due to orbital ferromagnetism. Gate voltages applied to the device can tune both the flatness and topology of the electronic bands, providing an unusual level of experimental control.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Bixuan Li, Juntian Wei, Chunqiao Jin, Kunpeng Si, Lingjia Meng, Xingguo Wang, Yangyu Jia, Qianqian He, Peng Zhang, Jinliang Wang, Yongji Gong
Summary: In this study, an intercalation strategy using organic molecules was developed to fabricate high-quality and diverse twisted bilayer graphene (tBLG). By weakening the interlayer interaction and inducing slide or rotation of the topmost graphene layer, the proportion of tBLGs in the resulting dtBLG reached up to 84.4% for twist angles ranging from 0 degrees to 30 degrees, surpassing previous methods. The twist angle distribution was found to be non-uniform, concentrating in the ranges of 0-10 degrees and 20-30 degrees. This facile and rapid intercalation-based methodology provides a practical solution for studying angle-dependent physics and advancing the utilization of twisted two-dimensional materials.
Article
Chemistry, Multidisciplinary
Matthieu Fortin-Deschenes, Rui Pu, Yan-Feng Zhou, Chao Ma, Patrick Cheung, Kenji Watanabe, Takashi Taniguchi, Fan Zhang, Xu Du, Fengnian Xia
Summary: In this study, using superconducting quantum interferometry, edge states with unusual moire band topology were discovered in twisted bilayer graphene.
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
Chemistry, Multidisciplinary
Minhao He, Jiaqi Cai, Ya-Hui Zhang, Yang Liu, Yuhao Li, Takashi Taniguchi, Kenji Watanabe, David H. Cobden, Matthew Yankowitz, Xiaodong Xu
Summary: Twisted double bilayer graphene has been studied as a platform for studying strongly correlated and topological states. In this research, a phase diagram representing these states as a function of parameters was constructed based on measurements of several devices. Symmetry-broken states were observed at a specific twist angle, including a Chern insulator state with band filling of 7/2 and an incipient state with filling of 11/3. An anomalous Hall effect was also observed at zero magnetic field in samples supporting the symmetry-broken states.
Article
Multidisciplinary Sciences
Bhaskar Ghawri, Phanibhusan S. Mahapatra, Manjari Garg, Shinjan Mandal, Saisab Bhowmik, Aditya Jayaraman, Radhika Soni, Kenji Watanabe, Takashi Taniguchi, H. R. Krishnamurthy, Manish Jain, Sumilan Banerjee, U. Chandni, Arindam Ghosh
Summary: When the relative rotation of twisted bilayer graphene is close to the magic angle, it exhibits interaction-driven phases with correlation-induced ground states and a possibility of non-Fermi liquid excitations. However, the manifestation of non-Fermi liquid effects in the transport properties of twisted bilayer graphene remains ambiguous.
NATURE COMMUNICATIONS
(2022)
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
Chemistry, Physical
Willem O. Tromp, Tjerk Benschop, Jian-Feng Ge, Irene Battisti, Koen M. Bastiaans, Damianos Chatzopoulos, Amber H. M. Vervloet, Steef Smit, Erik van Heumen, Mark S. Golden, Yinkai Huang, Takeshi Kondo, Tsunehiro Takeuchi, Yi Yin, Jennifer E. Hoffman, Miguel Antonio Sulangi, Jan Zaanen, Milan P. Allan
Summary: Superconductivity in high-doped cuprate superconductors is found to be qualitatively different from conventional mean-field theory, as the superfluid density vanishes when the transition temperature goes to zero, which contradicts expectations from Bardeen-Cooper-Schrieffer theory. Scanning tunnelling spectroscopy measurements reveal the emergence of nanoscale superconducting puddles in a metallic matrix, driven by gap filling instead of gap closing, indicating that the breakdown of superconductivity is not caused by diminishing pairing interaction.
Article
Multidisciplinary Sciences
Weijiong Chen, Clara Neerup Breio, Freek Massee, Milan P. Allan, Cedomir Petrovic, J. C. Seamus Davis, Peter J. Hirschfeld, Brian M. Andersen, Andreas Kreisel
Summary: The authors used scanning tunneling microscopy to detect the orbital order in the superconductor CeCoIn5, which is enhanced in the superconducting state as predicted. Visualization of atomic-orbital degrees of freedom is a challenge in scanned microscopy. Sublattice-resolved superconductive QPI techniques represent a new approach for studying hidden orbital order.
NATURE COMMUNICATIONS
(2023)
Article
Multidisciplinary Sciences
Jian-Feng Ge, Koen M. Bastiaans, Damianos Chatzopoulos, Doohee Cho, Willem O. Tromp, Tjerk Benschop, Jiasen Niu, Genda Gu, Milan P. Allan
Summary: The authors use local shot noise spectroscopy to investigate the charge transfer characteristics of zero-energy bound states in superconducting vortices and rule out the presence of impurity states. This study paves the way for investigating exotic states in vortex cores and future Majorana devices.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Tobias A. de Jong, Luuk Visser, Johannes Jobst, Ruud M. Tromp, Sense Jan van der Molen
Summary: Terrace-sized, single-orientation graphene can be grown on silicon carbide by thermal decomposition, but exhibits significant variation in electron transport properties. The moire pattern formed by lattice mismatch between the graphene and buffer layer leads to domain boundaries and edge dislocations. The coexistence of anisotropic stripe domains and isotropic trigonal domains causes intrinsic disorder in epitaxial graphene, and the growth process and substrate influence the domain orientation.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Xingchen Chen, Mio Poortvliet, Sense Jan van der Molen, Michiel J. A. de Dood
Summary: Researchers have successfully controlled the type of junction by stacking 2H-NbSe2 flakes and found that the shape of interference patterns is not only determined by the type of junction, but also by the magnetic field orientation and interface geometry.
Article
Materials Science, Multidisciplinary
Peter S. Neu, Makars Siskins, Eugene E. Krasovskii, Rudolf M. Tromp, Sense Jan van der Molen
Summary: In van der Waals (vdW) materials, the electron mean free path (MFP) is influenced by discrete states in the unoccupied band structure. However, measurements on vdW materials lack energy resolution except for graphene. In this study, reflection and transmission spectra of freestanding few-layered molybdenum disulfide (MoS2) samples were obtained, revealing enhanced electron transmissivity states above the vacuum level. A quantum-mechanical calculation confirmed an understanding of elastic scattering in MoS2, and a model was developed to extract the inelastic MFP spectrum.
Article
Materials Science, Multidisciplinary
Tobias A. de Jong, Xingchen Chen, Johannes Jobst, Eugene E. Krasovskii, Ruud M. Tromp, Sense Jan Molen
Summary: Stacking domain boundaries in Van der Waals heterostacks exhibit different contrast in BF-LEEM depending on their depth and size, with amplitude contrast being dominant for shallow boundaries between the top two graphene layers and phase contrast being strong for small domains. We derive a general rule-of-thumb for the expected BF-LEEM contrast of domain boundaries in Van der Waals materials.
