Article
Chemistry, Physical
Shuang Wu, Zhenyuan Zhang, K. Watanabe, T. Taniguchi, Eva Y. Andrei
Summary: In magic-angle twisted bilayer graphene, doping-induced Lifshitz transitions and van Hove singularities lead to the emergence of correlation-induced gaps and topologically non-trivial subbands. With the presence of a magnetic field, quantized Hall plateaus reveal the subband topology and signal the emergence of Chern insulators with Chern numbers. Additionally, a van Hove singularity at a filling of 3.5 suggests the possibility of a fractional Chern insulator, accompanied by a crossover from low-temperature metallic to high-temperature insulating behavior.
Article
Multidisciplinary Sciences
Yong Hu, Xianxin Wu, Yongqi Yang, Shunye Gao, Nicholas C. Plumb, Andreas P. Schnyder, Weiwei Xie, Junzhang Ma, Ming Shi
Summary: This study reveals the existence of topologically Dirac surface states (TDSSs) in the magnetic kagome material GdV6Sn6 and successfully manipulates the TDSSs and van Hove singularities (VHSs). These results provide a significant platform for studying the nontrivial topology, magnetism, and correlation effects in kagome lattices.
Article
Materials Science, Multidisciplinary
Zhengzhi Wu, Yi-Ming Wu, Fengcheng Wu
Summary: We show that the pair density wave (PDW) susceptibility can be enhanced to the same level as the BCS susceptibility through a valley-contrasting flux in moire systems. The PDW order becomes the leading instability under certain conditions, while a topological loop current order emerges if the Fermi surface with conventional Van Hove singularities is perfectly nested. The flux can be controlled experimentally in moire systems based on graphene and transition metal dichalcogenides.
Article
Physics, Multidisciplinary
Yin-Xiang Li, Xiao-Tong Yang
Summary: In this study, we found that Ni-based transition-metal trichalcogenides exhibit a suppression of chiral even-parity d + id-wave (E-g) state by odd-parity p + ip-wave (E-u) state when approaching the type-II van Hove singularities. The type-II van Hove singularities peak in density of states strengthens ferromagnetic fluctuation, leading to triplet pairing. The competition between antiferromagnetic and ferromagnetic fluctuation results in a pairing phase transition from singlet to triplet pairing in these materials.
FRONTIERS OF PHYSICS
(2021)
Article
Multidisciplinary Sciences
Harley D. Scammell, Julian Ingham, Tommy Li, Oleg P. Sushkov
Summary: Recent experiments on kagome metals AV(3)Sb(5) reveal the presence of twofold van Hove singularities (TvHS) near the Fermi energy, leading to the formation of two approximately hexagonal Fermi surfaces - one electron-like and the other hole-like. A TvHS is suggested to give rise to a novel time-reversal symmetry breaking excitonic order, caused by bound pairs of electrons and holes located at opposite concavity van Hove singularities. A minimal model for TvHS is introduced, and many-body instabilities induced by interactions are investigated using perturbative renormalisation group technique and free energy analysis. A phase diagram consisting of chiral excitons, charge density wave, and a coexistence region is constructed for the kagome metals AV(3)Sb(5), explaining various experimental observations. The chiral excitonic state leads to a quantum anomalous Hall conductance, providing an explanation for the observed anomalous Hall effect in kagome metals. Possible alternative realisations of the TvHS mechanism in bilayer materials are also discussed, suggesting that TvHS offer interesting possibilities for correlated phases, expanding the range of competing ground states to include excitonic order.
NATURE COMMUNICATIONS
(2023)
Article
Physics, Multidisciplinary
Daniel S. S. Sanchez, Tyler A. A. Cochran, Ilya Belopolski, Zi-Jia Cheng, Xian P. Yang, Yiyuan Liu, Tao Hou, Xitong Xu, Kaustuv Manna, Chandra Shekhar, Jia-Xin Yin, Horst Borrmann, Alla Chikina, Jonathan D. D. Denlinger, Vladimir N. N. Strocov, Weiwei Xie, Claudia Felser, Shuang Jia, Guoqing Chang, M. Zahid Hasan
Summary: The classification of electronic phases is based on two prominent paradigms: correlations and topology. Electron correlations lead to superconductivity and charge density waves, while the Berry phase gives rise to electronic topology. The combination of these two paradigms has prompted the search for electronic instabilities near the Fermi level of topological materials. This study identifies the electronic topology of chiral fermions as the driving force behind van Hove singularities that host electronic instabilities in the surface band structure.
Article
Materials Science, Multidisciplinary
J. Ebad-Allah, A. A. Tsirlin, Y. L. Zhu, Z. Q. Mao, C. A. Kuntscher
Summary: We conducted a temperature-dependent infrared spectroscopy study on the layered topological semimetal Nb3SiTe6 and performed density-functional theory calculations to investigate its electronic band structure and optical conductivity. Our results showed an anisotropic behavior of the in-plane optical conductivity, with three prominent excitations located at around 0.15, 0.28, and 0.41 eV when the incident radiation was polarized along the c axis. These excitations were well reproduced in the theoretical spectra. Based on the ab initio results, we interpreted the excitations around 0.15 and 0.28 eV as fingerprints of van Hove singularities in the electronic band structure and compared them to findings in other topological semimetals.
Article
Chemistry, Physical
Liangliang Liu, Chunyan Wang, Liying Zhang, Chengyan Liu, Chunyao Niu, Zaiping Zeng, Dongwei Ma, Yu Jia
Summary: This study explores the potential role of Surface Van Hove singularity (SVHS) in CO oxidation and the hydrogen evolution reaction (HER). It is demonstrated that systems with SVHS can promote CO oxidation and HER, and their catalytically active sites are distributed over the whole surface plane.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Jie Cao, Fenghua Qi, Yuanyuan Xiang, Guojun Jin
Summary: This paper investigates superconductivity in twisted bilayer graphene and develops a unified theoretical framework for electron-phonon coupling. Using experimental results as verification, the strongest superconductivity is found near the moire band filling factor of approximately 2. The pairing symmetry is strongly dependent on the filling factor, with different pairing states appearing in sequence.
Article
Materials Science, Multidisciplinary
Xinloong Han, Andreas P. Schnyder, Xianxin Wu
Summary: Motivated by the experimental identification of a higher-order Van Hove singularity (VHS) in AV3Sb5 kagome metals, this study investigates electronic instabilities of two-dimensional lattice models with higher-order VHS and flavor degeneracy. The larger power-law density of states and weaker nesting propensity of higher-order VHSs lead to distinct competing instabilities. Unbiased renormalization group calculations reveal a rich phase diagram containing ferromagnetism, antiferromagnetism, superconductivity, and Pomeranchuk orders. Notably, there is a generic transition from superconductivity to a d-wave Pomeranchuk order with increasing flavor number. Implications for the intriguing quantum states of AV3Sb5 kagome metals are also discussed.
Article
Physics, Multidisciplinary
Shuigang Xu, Mohammed M. Al Ezzi, Nilanthy Balakrishnan, Aitor Garcia-Ruiz, Bonnie Tsim, Ciaran Mullan, Julien Barrier, Na Xin, Benjamin A. Piot, Takashi Taniguchi, Kenji Watanabe, Alexandra Carvalho, Artem Mishchenko, A. K. Geim, Vladimir I. Fal'ko, Shaffique Adam, Antonio Helio Castro Neto, Kostya S. Novoselov, Yanmeng Shi
Summary: The study of electronic transport properties of twisted monolayer-bilayer graphene reveals highly tunable van Hove singularities that can cause strong correlation effects under optimum conditions by changing the twist angle or applying an electric field. This demonstrates the potential for correlated insulating states in a structure of monolayer and bilayer graphene with a small twist between them.
Article
Materials Science, Multidisciplinary
S. Ichinokura, M. Toyoda, M. Hashizume, K. Horii, S. Kusaka, S. Ideta, K. Tanaka, R. Shimizu, T. Hitosugi, S. Saito, T. Hirahara
Summary: We demonstrate a method to control the Fermi level around the Van Hove singularity (VHS) in Li-intercalated graphene on the SiC substrate. By observing a clear Lifshitz transition in the vicinity of the VHS when the thickness of graphene exceeds four layers, we calculate the band structure of a multilayer system with different stacking sequences of graphene and Li layer. Furthermore, a sizable Schottky barrier is formed between graphene and the substrate, allowing us to explore the electronic phase diagram around the VHS by controlling the thickness.
Article
Materials Science, Multidisciplinary
A. Kreisel, C. A. Marques, L. C. Rhodes, X. Kong, T. Berlijn, R. Fittipaldi, V. Granata, A. Vecchione, P. Wahl, P. J. Hirschfeld
Summary: The single-layered ruthenate Sr2RuO4 is a mysterious unconventional superconductor with an electronic structure affected by the van Hove singularity in its surface layer. Recent experiments indicate a singlet state, ruling out the original p-wave scenario and highlighting the importance of the van Hove singularity.
NPJ QUANTUM MATERIALS
(2021)
Article
Chemistry, Physical
Yang Sun, Zhen Zhang, Andrew P. Porter, Kirill Kovnir, Kai-Ming Ho, Vladimir Antropov
Summary: A computational search has identified a family of structurally stable or almost stable α-ATB4 compounds. These compounds are metallic in their non-magnetic states and exhibit localized molecular-like states and numerous singularities in the electronic spectrum. For certain elements, these singularities give rise to magnetic ground states with weak metallic or semiconducting nature.
NPJ COMPUTATIONAL MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Pierpaolo Fontana, Michele Burrello, Andrea Trombettoni
Summary: In three-dimensional topological metals, certain van Hove singularities are located precisely at the transitions between topological and trivial gapless phases, which are referred to as topological van Hove singularities. These singularities originate from energy saddle points between Weyl points with opposite chiralities, and their topological nature is illustrated through their magnetotransport properties. Analyzing the 3D Hofstadter model further exemplifies the relationship between van Hove singularities and topological phase transitions in Weyl systems.
Article
Physics, Multidisciplinary
Changhua Bao, Hongyun Zhang, Teng Zhang, Xi Wu, Laipeng Luo, Shaohua Zhou, Qian Li, Yanhui Hou, Wei Yao, Liwei Liu, Pu Yu, Jia Li, Wenhui Duan, Hong Yao, Yeliang Wang, Shuyun Zhou
Summary: Researchers have reported direct experimental evidence of chiral symmetry breaking (CSB) in Li-intercalated graphene, showing gap opening at the Dirac point, Kekule-O type modulation, and chirality mixing near the gap edge. This work opens up opportunities for investigating CSB related physics in a Kekule-ordered graphene.
PHYSICAL REVIEW LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Kevin S. Huang, Zhaoyu Han, Steven A. Kivelson, Hong Yao
Summary: In this study, a density-matrix renormalization-group study was conducted on PDW superconducting states on long triangular cylinders, revealing strong quasi-long-range PDW order, divergent PDW susceptibility, and the spontaneous breaking of time-reversal and inversion symmetries. The state was identified as valley-polarized and the PDW was found to arise from intra-pocket pairing with an incommensurate center of mass momentum. This study also observed an unusual realization of a Luther-Emery liquid in the two-leg case.
NPJ QUANTUM MATERIALS
(2022)
Article
Physics, Multidisciplinary
Shi-Xin Zhang, Zhou-Quan Wan, Chee-Kong Lee, Chang-Yu Hsieh, Shengyu Zhang, Hong Yao
Summary: The variational quantum-neural hybrid eigensolver (VQNHE) is introduced in this study, which enhances the shallow-circuit quantum Ansatz by combining classical post-processing with neural networks. Experimental results show that VQNHE consistently outperforms VQE in simulating ground-state energies of quantum spins and molecules, and it represents the first scalable method to exponentially accelerate VQE with nonunitary postprocessing efficiently implemented in the NISQ era.
PHYSICAL REVIEW LETTERS
(2022)
Article
Quantum Science & Technology
Shi-Xin Zhang, Chang-Yu Hsieh, Shengyu Zhang, Hong Yao
Summary: Quantum architecture search (QAS) automates the process of engineering quantum circuits and aims to construct a powerful and general platform that can accelerate the identification of quantum advantages. In this paper, we propose a general framework of differentiable quantum architecture search (DQAS) and demonstrate its capabilities in various circuit design problems. These results highlight the potential of DQAS as a valuable tool for NISQ application developments and present an interesting research topic from a theoretical perspective.
QUANTUM SCIENCE AND TECHNOLOGY
(2022)
Article
Physics, Multidisciplinary
Jin-Tao Jin, Kun Jiang, Hong Yao, Yi Zhou
Summary: This study demonstrates that spontaneous time-reversal symmetry breaking can arise naturally from the interaction between pair density wave ordering at multiple momenta and nesting of Fermi surfaces. The results have important implications for future experiments and real materials such as CsV3Sb5.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Shuo Liu, Shi-Xin Zhang, Chang-Yu Hsieh, Shengyu Zhang, Hong Yao
Summary: In this letter, a simple disorder-free periodically driven model is proposed that exhibits nontrivial discrete time crystal (DTC) order stabilized by Stark many-body localization (MBL). The existence of the DTC phase is demonstrated through analytical analysis and numerical evidence. This new DTC model opens up a new promising avenue for experiments and deepens our understanding of DTCs.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
Yi-Ming Wu, Zhengzhi Wu, Hong Yao
Summary: In this paper, we theoretically explore the possible orders induced by weak repulsive interactions in twisted bilayer transition metal dichalcogenides (e.g., WSe2) under an out-of-plane electric field. Our renormalization group analysis shows that superconductivity can survive even with the presence of conventional van Hove singularities. We find that topological chiral superconducting states with different Chern numbers appear over a large parameter region with a moiré filling factor around 1.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Shuo Liu, Shi-Xin Zhang, Chang -Yu Hsieh, Shengyu Zhang, Hong Yao
Summary: This study proposes a systematic approach to probe MBL phases using the excited-state variational quantum eigensolver (VQE) and demonstrates convincing results of MBL on a quantum hardware, paving a promising way for future simulations of nonequilibrium systems beyond classical computations in the noisy intermediate-scale quantum (NISQ) era.
Article
Physics, Multidisciplinary
Ming-Rui Li, Ai -Lei He, Hong Yao
Summary: This study proposes a twisted bilayer structure composed of 2D systems and investigates its stable quadratic-band-touching points and exotic physics. The research reveals that exactly flat bands can emerge at specific magic angles with high Chern numbers. Moreover, the effect of Coulomb interactions is considered, and the ground state supports the quantum anomalous Hall effect.
PHYSICAL REVIEW RESEARCH
(2022)
Article
Materials Science, Multidisciplinary
Zhou-Quan Wan, Shi-Xin Zhang, Hong Yao
Summary: As an unbiased method, the quantum Monte Carlo (QMC) method is important for simulating interacting quantum systems. However, it often suffers from the sign problem, which can be mitigated by finding better simulation schemes. In this study, researchers propose a general framework called automatic differentiable sign optimization (ADSO) to automatically search for the best QMC scheme within a given ansatz of the Hubbard-Stratonovich transformation. They apply ADSO to the honeycomb lattice Hubbard model with Rashba spin-orbit coupling and demonstrate its effectiveness in mitigating and even solving the sign problem.
Article
Materials Science, Multidisciplinary
Xun Cai, Zi-Xiang Li, Hong Yao
Summary: This article investigates the Su-Schrieffer-Heeger-Hubbard model and shows that Hubbard interactions can further enhance EPC-induced AFM effects, especially for small phonon frequencies or in adiabatic limit.
Article
Physics, Multidisciplinary
Xiaoyang Shen, Zhengzhi Wu, Linhao Li, Zhehan Qin, Hong Yao
Summary: This Letter investigates the fracton topological order of higher dimensional fracton models at nonzero critical temperature T-c, and demonstrates the existence of a finite critical temperature T-c. By analyzing the free energy of a typical 4D X-cube model using duality, it is shown that a finite critical temperature T-c exists. The expectation value of the 't Hooft loops in the 4D X-cube model reveals a confinement-deconfinement phase transition at finite temperature. Additionally, an alternative no-go theorem for finite-temperature quantum fracton topological order is proposed.
PHYSICAL REVIEW RESEARCH
(2022)
Article
Materials Science, Multidisciplinary
Z. X. Yin, X. Du, W. Z. Cao, J. Jiang, C. Chen, S. R. Duan, J. S. Zhou, X. Gu, R. Z. Xu, Q. Q. Zhang, W. X. Zhao, Y. D. Li, Yi-feng Yang, H. F. Yang, A. J. Liang, Z. K. Liu, H. Yao, Y. P. Qi, Y. L. Chen, L. X. Yang
Summary: This study systematically investigates the electronic structure of the archetypical valence fluctuating compound EuNi2P2, which hosts multiple f electrons, using high-resolution angle-resolved photoemission spectroscopy. The hybridization between Eu 4 f and Ni 3d states is revealed at low temperatures. Interestingly, opposite temperature evolution of electron spectral function above and below the Kondo coherence temperature is observed, which is in contrast to the monotonic valence change and beyond the expectation of the periodic Anderson model.
Article
Materials Science, Multidisciplinary
Ai-Lei He, Wei-Wei Luo, Yuan Zhou, Yi-Fei Wang, Hong Yao
Summary: In this study, two types of topological states are observed in an extended 2D dimerized lattice with staggered flux threading. At 1/2 filling, isolated corner states and metallic near-edge states are observed in the C = 2 Chern insulator states. At 1/4 filling, a C = 0 topological state is found, where the robust edge states are well localized along the edges but bypass corners. These topological insulator states differ from both conventional Chern insulators and the usual high-order topological insulators.
Article
Computer Science, Artificial Intelligence
Shi-Xin Zhang, Chang-Yu Hsieh, Shengyu Zhang, Hong Yao
Summary: Variational quantum algorithms (VQAs) are speculated to provide quantum advantages for practical problems, with Quantum Architecture Search (QAS) being a method to design task-specific Parameterized Quantum Circuits (PQCs). A neural predictor guided QAS is shown to discover powerful quantum circuit solutions, outperforming random search baselines and capable of generalizing to address similar problems.
MACHINE LEARNING-SCIENCE AND TECHNOLOGY
(2021)
