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arXiv 2022年

作者： Dey, Arjun Najita, Joan R. Koposov, Sergey E. Josephy-Zack, J. Maxemin, Gabriel Bell, Eric F. Poppett, C. Patel, E. Silva, L.E. Beraldo Raichoor, A. Schlegel, D. Lang, D. Meisner, A. Myers, Adam D. Aguilar, J. Ahlen, S. Prieto, C. Allende Brooks, D. Cooper, A.P. Dawson, K.S. de la Macorra, A. Doel, P. Font-Ribera, A. García-Bellido, Juan Gontcho, S.A. Gontcho Guy, J. Honscheid, K. Kehoe, R. Kisner, T. Kremin, A. Landriau, M. Guillou, L. Le Levi, Michael E. Li, T.S. Martini, Paul Miquel, R. Moustakas, J. Nie, Jundan Palanque-Delabrouille, N. Prada, F. Schlafly, E.F. Sharples, Ray M. Tarlé, Gregory Ting, Yuan-Sen Tyas, L. Valluri, M. Wechsler, Risa H. Zou, H. NSF’s NOIRLab 950 N. Cherry Avenue TucsonAZ85719 United States Institute for Astronomy University of Edinburgh Royal Observatory Blackford Hill EdinburghEH9 3HJ United Kingdom Institute of Astronomy University of Cambridge Madingley road CambridgeCB3 0HA United Kingdom Harvard College CambridgeMA02138 United States Department of Astronomy University of Michigan Ann ArborMI48109 United States Lawrence Berkeley National Laboratory 1 Cyclotron Road BerkeleyCA94720 United States Space Sciences Laboratory University of California Berkeley 7 Gauss Way BerkeleyCA94720 United States University of California Berkeley 110 Sproul Hall #5800 BerkeleyCA94720 United States Astronomy Dept. University of California at Berkeley BerkeleyCA94720 United States Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Perimeter Institute for Theoretical Physics 31 Caroline Street N WaterlooONN25 2YL Canada Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada Department of Physics & Astronomy University of Wyoming 1000 E. University Dept. 3905 LaramieWY82071 United States Physics Dept. Boston University 590 Commonwealth Avenue BostonMA02215 United States Instituto de Astrofísica de Canarias C/ Vía Láctea s/n San Cristóbal de La Laguna Santa Cruz de Tenerife38205 Spain Department of Physics & Astronomy University College London Gower Street LondonWC1E 6BT United Kingdom Institute of Astronomy Department of Physics National Tsing Hua University 101 Kuang-Fu Rd. Sec. 2 Hsinchu30013 Taiwan Center for Informatics and Computation in Astronomy NTHU 101 Kuang-Fu Rd. Sec. 2 Hsinchu30013 Taiwan Physics Division National Center for Theoretical Sciences Taipei10617 Taiwan Department of Physics and Astronomy The University of Utah 115 South 1400 East Salt Lake CityUT84112 United States Instituto de Física Universidad Nacional Autónoma de México Cd. de MéxicoC.P. 04510 Mexico The Barcelona Institu

We present Dark Energy Spectroscopic Instrument (DESI) observations of the inner halo of M31, which reveal the kinematics of a recent merger—a galactic immigration event—in exquisite detail. Of the 11,416 sources studied in 3.75 hr of on-sky exposure time, 7,438 are M31 sources with well-measured radial velocities. The observations reveal intricate coherent kinematic structure in the positions and velocities of individual stars: streams, wedges, and chevrons. While hints of coherent structures have been previously detected in M31, this is the first time they have been seen with such detail and clarity in a galaxy beyond the Milky Way. We find clear kinematic evidence for shell structures in the Giant Stellar Stream, the Northeast Shelf and Western Shelf regions. The kinematics are remarkably similar to the predictions of dynamical models constructed to explain the spatial morphology of the inner halo. The results are consistent with the interpretation that much of the substructure in the inner halo of M31 is produced by a single galactic immigration event 1–2 Gyr ago. Significant numbers of metal-rich stars ([Fe/H] > −0.5) are present in all of the detected substructures, suggesting that the immigrating galaxy had an extended star formation history. We also investigate the ability of the shells and Giant Stellar Stream to constrain the gravitational potential of M31, and estimate the mass within a projected radius of 125 kpc to be log10 MNFW(+−001210. The results herald a new era in our ability to study stars on a galactic scale and the immigration histories of galaxies. © 2022, CC BY.

关键词： Galaxies

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Valence Bond Orders at Charge Neutrality in a Possible Two-Orbital Extended Hubbard Model for Twisted Bilayer Graphene

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Physical Review Letters 2019年第15期123卷 157601-157601页

作者： Yuan Da Liao Zi Yang Meng Xiao Yan Xu Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing 100190 China Department of Physics and HKU-UCAS Joint Institute of Theoretical and Computational Physics The University of Hong Kong Pokfulam Road Hong Kong China Songshan Lake Materials Laboratory Dongguan Guangdong 523808 China CAS Center of Excellence in Topological Quantum Computation and School of Physical Sciences University of Chinese Academy of Sciences Beijing 100190 China Department of Physics Hong Kong University of Science and Technology Clear Water Bay Hong Kong China Department of Physics University of California at San Diego La Jolla California 92093 USA

An extended Hubbard model on a honeycomb lattice with two orbitals per site at charge neutrality is investigated with unbiased large-scale quantum Monte Carlo simulations. The Fermi velocity of the Dirac fermions is renormalized as the cluster charge interaction increases, until a mass term emerges and a quantum phase transition from Dirac semimetal to valence bond solid (VBS) insulator is established. The quantum critical point is discovered to belong to the 3D N=4 Gross-Neveu chiral XY universality with the critical exponents obtained at high precision. Further enhancement of the interaction drives the system into two different VBS phases, the properties and transition between them are also revealed. Since the model is related to magic-angle twisted bilayer graphene, our results may have relevance towards the symmetry breaking order at the charge neutrality point of the material, and associate the wide range of universal strange metal behavior around it with quantum critical fluctuations.

关键词： Dirac fermions Order parameters Quantum phase transitions Quantum spin Hall effect Bilayer films Dirac semimetal Graphene Strongly correlated systems Electron-correlation calculations Quantum Monte Carlo

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Parton distribution functions of ∆+ on the lattice

arXiv

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arXiv 2020年

作者： Chai, Yahui Li, Yuan Xia, Shicheng Alexandrou, Constantia Cichy, Krzysztof Constantinou, Martha Feng, Xu Hadjiyiannakou, Kyriakos Jansen, Karl Koutsou, Giannis Liu, Chuan Scapellato, Aurora Steffens, Fernanda School of Physics Peking University Beijing100871 China Department of Physics University of Cyprus P.O. Box 20537 Nicosia1678 Cyprus Computation-based Science and Technology Research Center Cyprus Institute 20 Kavafi Str. Nicosia2121 Cyprus Faculty of Physics Adam Mickiewicz University ul. Uniwersytetu Pozná nskiego 2 Pozná n61-614 Poland Temple University 1925 N. 12th Street PhiladelphiaPA19122-1801 United States Collaborative Innovation Center of Quantum Matter Beijing100871 China Center for High Energy Physics Peking University Beijing100871 China State Key Laboratory of Nuclear Physics and Technology Peking University Beijing100871 China NIC DESY Platanenallee 6 ZeuthenD-15738 Germany Institut für Strahlen- und Kernphysik Rheinische Friedrich-Wilhelms-Universität Bonn Nussallee 14-16 Bonn53115 Germany

We perform a first calculation for the unpolarized parton distribution function of the ∆+ baryon using lattice QCD simulations within the framework of Large Momentum Effective Theory. Two ensembles of Nf = 2 + 1 + 1 twisted mass fermions are utilized with a pion mass of 270 MeV and 360 MeV, respectively. The baryon is boosted with momentum P3 with values {0.42, 0.83, 1.25} GeV, and we utilize momentum smearing to improve the signal. The physical unpolarized parton distribution function of ∆+ is obtained using a non-perturbative renormalization and_a one-loop formula for the matching, with encouraging precision. In particular, we compute the d(x) − u(x) asymmetry and compare it with the same quantity in the nucleon, in a first attempt to resolve the physical mechanism responsible for generating such asymmetry. Copyright © 2020, The Authors. All rights reserved.

关键词： Hadrons

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Ferromagnetism-induced Kondo effect in graphene with a magnetic impurity

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Physical Review B 2019年第11期100卷 115115-115115页

作者： Gao-Yang Li Tie-Feng Fang Ai-Min Guo Qing-Feng Sun School of Physical Science and Technology Lanzhou University Lanzhou 730000 China Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of Physics and Electronics Central South University Changsha 410083 China International Center for Quantum Materials School of Physics Peking University Beijing 100871 China Collaborative Innovation Center of Quantum Matter Beijing 100871 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China

We investigate the many-body effects of a magnetic adatom in ferromagnetic graphene by using the numerical renormalization group method. The nontrivial band dispersion of ferromagnetic graphene gives rise to interesting Kondo physics different from that in conventional ferromagnetic materials. For a half-filled impurity in undoped graphene, the presence of ferromagnetism can bring forth Kondo correlations, yielding two kink structures in the local spectral function near the Fermi energy. When the spin splitting of local occupations is compensated by an external magnetic field, the two Kondo kinks merge into a full Kondo resonance characterizing the fully screened ground state. Strikingly, we find the resulting Kondo temperature monotonically increases with the spin polarization of Dirac electrons, which violates the commonsense belief that ferromagnetic bands are usually detrimental to Kondo correlations. Doped ferromagnetic graphene can behave as half-metals, where its density of states at the Fermi energy linearly vanishes for one spin direction but remains finite for the opposite direction. In this regime, we demonstrate an abnormal Kondo resonance that occurs in the first spin direction but is completely absent in the other one.

关键词： Ferromagnetism Kondo effect Graphene Anderson impurity model Numerical Renormalization Group

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Parton distribution functions of ∆+ on the lattice 37

Parton distribution functions of ∆+ on the lattice

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37th International Symposium on Lattice Field Theory, LATTICE 2019

作者： Chai, Yahui Li, Yuan Xia, Shicheng Alexandrou, Constantia Cichy, Krzysztof Constantinou, Martha Feng, Xu Hadjiyiannakou, Kyriakos Jansen, Karl Koutsou, Giannis Liu, Chuan Scapellato, Aurora Steffens, Fernanda School of Physics Peking University Beijing100871 China Computation-based Science and Technology Research Center Cyprus Institute 20 Kavafi Str. Nicosia2121 Cyprus Faculty of Physics Adam Mickiewicz University Umultowska 85 Pozná n61-614 Poland Temple University 1925 N. 12th Street PhiladelphiaPA19122-1801 United States Department of Physics University of Cyprus P.O. Box 20537 Nicosia1678 Cyprus Collaborative Innovation Center of Quantum Matter Beijing100871 China Center for High Energy Physics Peking University Beijing100871 China State Key Laboratory of Nuclear Physics and Technology Peking University Beijing100871 China NIC DESY Platanenallee 6 ZeuthenD-15738 Germany Department of Physics Bergische Universiẗt Wuppertal Gaussstr. 20 Wuppertal42119 Germany Institut für Strahlen- und Kernphysik Rheinische Friedrich-Wilhelms-Universität Bonn Nussallee 14-16 Bonn53115 Germany

We present results for renormalized matrix elements related to the unpolarized quasi-distribution function of the ∆+ baryon making use of the large momentum effective theory. Two ensembles of Nf = 2 + 1 + 1 twisted mass fermions with a clover term and pion masses of 250 MeV and 330 MeV are analyzed. We employ momentum smearing to improve the overlap with the boosted ∆ state significantly reducing in this way the statistical error of both two- and three-point functions. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0).

关键词： Distribution functions

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Observation of energy resolved many-body localization

arXiv

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arXiv 2019年

作者： Guo, Qiujiang Cheng, Chen Sun, Zheng-Hang Song, Zixuan Li, Hekang Wang, Zhen Ren, Wenhui Dong, Hang Zheng, Dongning Zhang, Yu-Ran Mondaini, Rubem Fan, Heng Wang, H. Interdisciplinary Centre for Quantum Information and Zhejiang Province Key Laboratory of Quantum Technology and Device Department of Physics Zhejiang University Hangzhou310027 China School of Physical Science and Technology Lanzhou University Lanzhou730000 China Beijing Computational Science Research Center Beijing100094 China Institute of Physics Chinese Academy of Sciences Beijing100190 China CAS Center for Excellence in Topological Quantum Computation School of Physical Sciences UCAS Beijing100190 China Theoretical Quantum Physics Laboratory RIKEN Cluster for Pioneering Research Wako-shi Saitama351-0198 Japan

Many-body localization (MBL) describes a quantum phase where an isolated interacting system subject to sufficient disorder displays non-ergodic behavior, evading thermal equilibrium that occurs under its own dynamics. Previously, the thermalization-MBL transition has been largely characterized with the growth of disorder. Here, we explore a new axis, reporting on an energy resolved MBL transition using a 19-qubit programmable superconducting processor, which enables precise control and flexibility of both disorder strength and initial state preparations. We observe that the onset of localization occurs at different disorder strengths, with distinguishable energy scales, by measuring time-evolved observables and many-body wavefunctions related quantities. Our results open avenues for the experimental exploration of many-body mobility edges in MBL systems, whose existence is widely debated due to system size finiteness, and where exact simulations in classical computers become unfeasible. Copyright © 2019, The Authors. All rights reserved.

关键词： Quantum theory

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Tight bounds for private communication over bosonic Gaussian channels based on teleportation simulation with optimal finite resources

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Physical Review A 2019年第4期100卷 042301-042301页

作者： Riccardo Laurenza Spyros Tserkis Leonardo Banchi Samuel L. Braunstein Timothy C. Ralph Stefano Pirandola Department of Computer Science University of York York YO10 5GH United Kingdom QSTAR INO-CNR and LENS Largo Enrico Fermi 2 50125 Firenze Italy Centre for Quantum Computation and Communication Technology School of Mathematics and Physics University of Queensland St Lucia Queensland 4072 Australia Department of Physics and Astronomy University of Florence via G. Sansone 1 I-50019 Sesto Fiorentino (FI) Italy Research Laboratory of Electronics Massachusetts Institute of Technology (MIT) Cambridge Massachusetts 02139 USA

Upper bounds for private communication over quantum channels can be derived by adopting channel simulation, protocol stretching, and relative entropy of entanglement. All these ingredients have led to single-letter upper bounds to the secret-key capacity which can be directly computed over suitable resource states. For bosonic Gaussian channels, the tightest upper bounds have been derived by employing teleportation simulation over asymptotic resource states, namely, the asymptotic Choi matrices of these channels. In this work, we adopt a different approach. We show that teleporting over an analytical class of finite-energy resource states allows us to closely approximate the ultimate bounds for increasing energy, so as to provide increasingly tight upper bounds to the secret-key capacity of one-mode phase-insensitive Gaussian channels. We then show that an optimization over the same class of resource states can be used to bound the maximum secret-key rates that are achievable in a finite number of channel uses.

关键词： Quantum channels Quantum communication Quantum cryptography Quantum teleportation

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Role of anion in the pairing interaction of iron-based superconductivity

arXiv

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arXiv 2020年

作者： Yin, Jiaxin Zhao, Y.Y. Wu, Zheng Wu, X.X. Kreisel, A. Andersen, B.M. Macam, Gennevieve Zhou, Sen Wu, Rui Liu, Limin Deng, Hanbin Zhu, Changjiang Li, Yuan Sun, Yingkai Huang, Zhi-Quan Chuang, Feng-Chuan Lin, Hsin Ting, C.-S. Hu, J.-P. Wang, Z.Q. Dai, P.C. Ding, H. Pan, S.H. Institute of Physics Chinese Academy of Sciences Beijing100190 China School of Physics and Optoelectronic Engineering Nanjing University of Information Science and Technology Nanjing210044 China TCSUH Department of Physics University of Houston HoustonTX77204 United States Institut für Theoretische Physik Universität Leipzig LeipzigD-04103 Germany Niels Bohr Institute University of Copenhagen Jagtvej 128 CopenhagenDK-2200 Denmark Department of Physics National Sun Yat-sen University Kaohsiung80424 Taiwan Institute of Theoretical Physics Chinese Academy of Sciences Beijing100190 China Institute of Physics Academia Sinica Taipei 11529 Taiwan Department of Physics Boston College Chestnut HillMA02467 United States Department of Physics and Astronomy Rice University HoustonTX77005 United States School of Physics University of Chinese Academy of Sciences Beijing100190 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing100190 China Songshang Lake Material Laboratory DongguanGuangdong523808 China

High-temperature iron-based superconductivity develops in a structure with unusual lattice-orbital geometry, based on a planar layer of Fe atoms with 3d orbitals and tetrahedrally coordinated by anions. Here we elucidate the electronic role of anions in the iron-based superconductors utilizing state-of-the-art scanning tunneling microscopy. By measuring the local electronic structure, we find that As anion in Ba0.4K0.6Fe2As2 has a striking impact on the electron pairing. The superconducting electronic feature can be switched off/on by removing/restoring As atoms on Fe layer at the atomic scale. Our analysis shows that this remarkable atomic switch effect is related to the geometrical cooperation between anion mediated hopping and unconventional pairing interaction. Our results uncover that the local Fe-anion coupling is fundamental for the pairing interaction of iron-based superconductivity, and promise the potential of bottom-up engineering of electron pairing. © 2020, CC-BY.

关键词： Negative ions

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GKZ-hypergeometric systems for Feynman integrals

arXiv

引用

arXiv 2019年

作者： Feng, Tai-Fu Chang, Chao-Hsi Chen, Jian-Bin Zhang, Hai-Bin Department of Physics Hebei University Baoding071002 China Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory Baoding071002 China Key Laboratory of Theoretical Physics Institute of Theoretical Physics Chinese Academy of Science Beijing100190 China P.O.Box 8730 Beijing100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing100049 China Department of Physics Taiyuan University of Technology Taiyuan030024 China Department of Physics Chongqing University Chongqing401331 China

Basing on the systems of linear partial differential equations derived from Mellin-Barnes representations and Miller’s transformation, we obtain GKZ-hypergeometric systems of one-loop self energy, one-loop triangle, two-loop vacuum, and two-loop sunset diagrams, respectively. The codimension of derived GKZ-hypergeometric system equals the number of independent dimensionless ratios among the external momentum squared and virtual mass squared. Taking GKZ-hypergeometric systems of one-loop self energy, massless one-loop triangle, and two-loop vacuum diagrams as examples, we present in detail how to perform triangulation and how to construct canonical series solutions in the corresponding convergent regions. The series solutions constructed for these hypergeometric systems recover the well known results in literature. Copyright © 2019, The Authors. All rights reserved.

关键词： Linear transformations

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Deriving models for the Kitaev spin-liquid candidate material α−RuCl3 from first principles

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Physical Review B 2019年第7期100卷 075110-075110页

作者： Casey Eichstaedt Yi Zhang Pontus Laurell Satoshi Okamoto Adolfo G. Eguiluz Tom Berlijn Department of Physics and Astronomy University of Tennessee Knoxville Tennessee 37996 USA Joint Institute of Advanced Materials University of Tennessee Knoxville Tennessee 37996 USA Department of Physics and Astronomy Louisiana State University Baton Rouge Louisiana 70803 USA Center for Computation and Technology Louisiana State University Baton Rouge Louisiana 70803 USA Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Computational Sciences and Engineering Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA

We use the constrained random phase approximation to derive from first principles the Ru-t2g Wannier-function-based model for the Kitaev spin-liquid candidate material α−RuCl3. We find the nonlocal Coulomb repulsion to be sizable compared to the local one. In addition we obtain the contribution to the Hamiltonian from the spin-orbit coupling and find it to also contain non-negligible nonlocal terms. We invoke strong-coupling perturbation theory to investigate the influence of these nonlocal elements of the Coulomb repulsion and the spin-orbit coupling on the magnetic interactions. We find that the nonlocal Coulomb repulsions cause a strong enhancement of the magnetic interactions, which deviate from experimental fits reported in the literature. Our results contribute to the understanding and design of quantum spin-liquid materials via first-principles calculations.

关键词： Quantum spin liquid Density functional theory Kitaev model Wannier function methods

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