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Maximally localized exciton wannier functions for solids

Physical Review B 2023年第12期108卷 125118-125118页

作者： Jonah B. Haber Diana Y. Qiu Felipe H. da Jornada Jeffrey B. Neaton Department of Physics University of California Berkeley Berkeley California 94720 USA Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA Department of Mechanical Engineering and Materials Science Yale University New Haven Connecticut 06520 USA Energy Science Institute Yale University New Haven Connecticut 06520 USA Department of Materials Science and Engineering Stanford University Stanford California 94305 USA Kavli Energy Nanosciences Institute Berkeley California 94720 USA

We introduce a maximally localized wannier function representation of Bloch excitons, two-particle correlated electron-hole excitations, in crystalline solids, where the excitons are maximally localized with respect to an average electron-hole coordinate in real space. As a proof-of-concept, we illustrate this representation in the case of low-energy spin-singlet and -triplet excitons in cubic lithium fluoride, computed using the ab initio Bethe-Salpeter equation approach. We visualize the resulting maximally localized exciton wannier functions (MLXWFs) in real space, detail the convergence of the exciton wannier spreads, and demonstrate how wannier-Fourier interpolation can be leveraged to obtain exciton energies and states at arbitrary exciton crystal momenta in the Brillouin zone. We further introduce an approach to treat the long-range dipolar coupling between singlet MLXWFs and discuss it in depth. The MLXWF representation sheds light on the fundamental nature of excitons and paves the way toward wannier-based post-processing of excitonic properties, enabling the construction of ab initio exciton tight-binding models, efficient interpolation of the exciton-phonon vertex, the computation of Berry curvature associated with exciton bands, and beyond.

关键词： Bethe-Salpeter equation Excitons wannier function methods

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Ideal hourglass-type charge-three Weyl fermions in spinless systems

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Physical Review B 2024年第7期109卷 075160-075160页

作者： Xiaoliang Xiao Yuanjun Jin Da-Shuai Ma Weixiang Kong Jing Fan Rui Wang Xiaozhi Wu Institute for Structure and Function & Department of Physics Chongqing University Chongqing 400044 People's Republic of China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore Center of Quantum Materials and Devices Chongqing University Chongqing 400044 People's Republic of China Center for Computational Science and Engineering Southern University of Science and Technology Shenzhen 518055 People's Republic of China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing 400044 People's Republic of China

Hourglass-type Weyl fermions with the maximally topological charge of |C|=3, namely hourglass-type charge-three Weyl fermions (CTWFs), have seldom been reported due to the nonnegligible spin-orbit coupling effect and Pauli exclusion principles. Here, based on symmetry arguments and the low-energy effective k·p model, we confirm that two chiral space groups (SGs), i.e., SG P63 (No. 173) and SG P6322 (No. 182), can host ideal hourglass-type CTWFs in spinless systems. Moreover, we take Li2CO4 as a concrete example to show the ideal hourglass-type CTWFs, which possess ultralong sextuple- and triple-helicoid Fermi arcs, making them easier to be detected by experiments. Our work not only offers an avenue to search for ideal hourglass-type CTWFs but also provides a promising platform for experiments to verify this kind of unconventional quasiparticles with the ultralong sextuple- and triple-helicoid surface arcs.

关键词： Electronic structure Fermions First-principles calculations Symmetry protected topological states 3-dimensional systems Crystal structures Weyl semimetal High-throughput calculations Symmetries in condensed matter wannier function methods k dot p method

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Effect of realistic out-of-plane dopant potentials on the superfluid density of overdoped cuprates

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Physical Review B 2022年第18期106卷 184510-184510页

作者： H. U. Özdemir Vivek Mishra N. R. Lee-Hone Xiangru Kong T. Berlijn D. M. Broun P. J. Hirschfeld Department of Physics Simon Fraser University Burnaby Canada BC V5A 1S6 Kavli Institute for Theoretical Sciences University of Chinese Academy of Sciences Beijing 100190 China Center For Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Department of Physics University of Florida Gainesville Florida 32611 USA

Recent experimental papers on hole-doped overdoped cuprates have argued that a series of observations showing unexpected behavior in the superconducting state imply the breakdown of the quasiparticle-based Landau–BCS paradigm in that doping range. In contrast, some of the present authors have argued that a phenomenological “dirty d-wave” theoretical analysis explains essentially all aspects of thermodynamic and transport properties in the superconducting state, provided the unusual effects of weak, out-of-plane dopant impurities are properly accounted for. Here we attempt to place this theory on a more quantitative basis by performing ab initio calculations of dopant impurity potentials for LSCO and Tl-2201. These potentials are more complex than the pointlike impurity models considered previously, and require calculation of forward scattering corrections to transport properties. Including realistic, ARPES-derived band structures, Fermi liquid renormalizations, and vertex corrections, we show that the theory can explain semiquantitatively the unusual superfluid density measurements of the two most studied overdoped materials.

关键词： First-principles calculations Impurities in superconductors Superconductivity Superfluid density BCS theory Density functional theory Fermi liquid theory wannier function methods

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Controlling topology through targeted composite symmetry manipulation in magnetic systems

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Physical Review B 2024年第20期110卷 205104页

作者： Ilyoun Na Marc Vila Sinéad M. Griffin Department of Physics Materials Sciences Division Molecular Foundry

The possibility of selecting magnetic space groups by orienting the magnetization direction or tuning magnetic orders offers a vast playground for engineering symmetry-protected topological phases in magnetic materials. In this work, we study how selective tuning of symmetry and magnetism can influence and control the resulting topology in a two-dimensional magnetic system, and we illustrate such a procedure in the ferromagnetic monolayer MnPSe3. Density functional theory calculations reveal a symmetry-protected accidental semimetallic (SM) phase for out-of-plane magnetization, which becomes an insulator when the magnetization is tilted in-plane, reaching band-gap values close to 100 meV. We identify an order-2 composite antiunitary symmetry and threefold rotational symmetry that induce the band crossing, and we classify the possible topological phases using symmetry analysis, which we support with tight-binding and k·p models. Breaking of inversion symmetry opens a gap in the SM phase, giving rise to a Chern insulator. We demonstrate this explicitly in the isostructural Janus compound Mn2P2S3Se3, which naturally exhibits Rashba spin-orbit coupling that breaks inversion symmetry. Our results map out the phase space of topological properties of ferromagnetic transition-metal phosphorus trichalcogenides, and they demonstrate the potential of the magnetization-dependent metal-to-insulator transition as a spin switch in integrated two-dimensional electronics.

关键词： Magnetic order Symmetry protected topological states Topological materials Two-dimensional electron system First-principles calculations Tight-binding model wannier function methods k dot p method

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Topological edge and corner states in the biphenylene network

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Physical Review B 2024年第3期109卷 035431-035431页

作者： Keiki Koizumi Huyen Thanh Phan Kento Nishigomi Katsunori Wakabayashi Department of Nanotechnology for Sustainable Energy School of Science and Technology Kwansei Gakuin University Gakuen-Uegahara 1 Sanda 669-1330 Japan National Institute for Materials Science Namiki 1-1 Tsukuba 305-0044 Japan Center for Spintronics Research Network Osaka University Toyonaka 560-8531 Japan

The electronic states and topological properties of the biphenylene network (BPN) are analyzed using a tight-binding model based on the π-electron network. It is shown that tuning the hopping parameters induces topological phase transitions, leading to the emergence of edge states owing to the nontrivial topological Zak phase of the bulk BPN. Elementary band analysis clearly gives the number of edge states, which are associated with the location of wannier centers. In addition, we present the conditions for the emergence of corner states owing to the higher-order topological nature of the BPN.

关键词： Edge states Electronic structure First-principles calculations Flat bands Surface states Topological materials 2-dimensional systems Graphene Nanoribbon Band structure methods Density functional theory Su-Schrieffer-Heeger model Tight-binding model wannier function methods

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Correlation between electronic polarization and shift current in cubic and hexagonal semiconductors LiZnX (X=P,As,Sb)

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Physical Review Materials 2024年第2期8卷 025001-025001页

作者： Urmimala Dey Jeroen van den Brink Rajyavardhan Ray Centre for Materials Physics Durham University South Road Durham DH1 3LE United Kingdom Leibniz IFW Dresden Helmholtzstr. 20 Dresden 01069 Germany Dresden Center for Computational Materials Science (DCMS) TU Dresden Dresden 01062 Germany Institute of Theoretical Physics and Würzburg-Dresden Cluster of Excellence ct.qmat Technische Universität Dresden 01062 Dresden Germany Department of Physics Birla Institute of Technology Mesra Ranchi 835215 Jharkhand India

The rectified bulk photovoltaic effect (BPVE) in noncentrosymmetric semiconductors, also called shift current, is considered promising for optoelectronic devices, terahertz emission, and possibly solar energy harvesting. A clear understanding of the shift current mechanism and search for materials with large shift current is, therefore, of immense interest. ABC semiconductors LiZnX (X=N, P, As, and Sb) can be stabilized in cubic as well as hexagonal morphologies lacking inversion symmetry—an ideal platform to investigate the significant contributing factors to shift current, such as the role of structure and chemical species. Using density-functional calculations properly accounting for the electronic bandgaps, the shift current conductivities in LiZnX (X=P, As, Sb) are found to be approximately an order of magnitude larger than the well-known counterparts and peak close to the maximum solar radiation intensity. Notably, hexagonal LiZnSb shows a peak shift current conductivity of about −75μA/V2 and Glass coefficient of about −20×10−8 cm/V, comparable to the highest predicted values in literature. Our comparative analysis reveals a quantitative relationship between the shift current response and the electronic polarization. These findings not only posit Li-Zn-based ABC semiconductors as viable material candidates for potential applications but also elucidates key aspects of the structure-BPVE relationship.

关键词： Density of states Electric polarization Electronic structure First-principles calculations Optical conductivity Ferroelectrics Piezoelectrics Density functional theory wannier function methods

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Prediction of monolayered ferromagnetic CrMnI6 as an intrinsic high-temperature quantum anomalous Hall system

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Physical Review B 2020年第11期102卷 115413-115413页

作者： Huisheng Zhang Wenjia Yang Ping Cui Xiaohong Xu Zhenyu Zhang Key Laboratory of Magnetic Molecules and Magnetic Information Materials of the Ministry of Education and Research Institute of Materials Science Shanxi Normal University Linfen 041004 China International Center for Quantum Design of Functional Materials (ICQD) Hefei National Laboratory for Physical Sciences at Microscale and CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Hefei Anhui 230026 China Key Laboratory of Strongly-Coupled Quantum Matter Physics Chinese Academy of Sciences School of Physical Sciences University of Science and Technology of China Hefei Anhui 230026 China

Quantized Hall conductance without an external magnetic field, known as the quantum anomalous Hall effect (QAHE), may have important applications in dissipationless spintronics, yet to date, it has only been realized in magnetically doped topological insulators and at very low temperatures. Here we design a physically realistic system for realizing QAHE by expanding the recently discovered two-dimensional ferromagnetic insulators as a new class of candidate materials. Based on first-principles calculations, we predict that a CrMnI6 monolayer is energetically stable and can be readily exfoliated. This system is further shown to be a ferromagnetic insulator, with a transition temperature of ∼87K, higher than that of CrI3. Most strikingly, such a monolayer is characterized as an intrinsic QAHE system with a high Chern number of C = 2, and the underlying mechanism for the nontrivial topology is attributed to the two inequivalent subset sites of the Cr and Mn atoms. The present study thus provides an ideal platform for realizing high-temperature QAHE beyond the prevailing materials class of magnetically doped topological insulators.

关键词： First-principles calculations Topological materials 2-dimensional systems Ferromagnets Density functional theory wannier function methods k dot p method

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Spin-polarized topological phases in a ferromagnetic Bi2Te3/MnBi2Te4 bilayer tuned by electric and magnetic fields

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Physical Review B 2022年第12期105卷 125126-125126页

作者： Shi Xiao Xiaoliang Xiao Fangyang Zhan Jing Fan Xiaozhi Wu Rui Wang Institute for Structure and Function and Department of Physics Chongqing University Chongqing 400044 People's Republic of China Chongqing Key Laboratory for Strongly Coupled Physics Chongqing 400044 People's Republic of China Center for Computational Science and Engineering Southern University of Science and Technology Shenzhen 518055 People's Republic of China Center of Quantum Materials and Devices Chongqing University Chongqing 400044 People's Republic of China

Applying electric or magnetic fields is widely used to not only create and manipulate topological states but also facilitate their observations in experiments. In this paper, we show by first-principles calculations and topological analysis that the time-reversal (TR) symmetry-broken quantum spin Hall (QSH) phase emerges in a two-dimensional (2D) ferromagnetic Bi2Te3/MnBi2Te4 bilayer. This TR-symmetry broken QSH phase possesses a highly tunable nontrivial band gap under external electric fields (or tuning interlayer distance). Furthermore, based on the wannier-function-based tight-binding approach, we reveal that a topological phase transition from the TR-symmetry broken QSH phase to the quantum anomalous Hall (QAH) phase occurs with the increase of magnetic fields. Besides, we also find that a reverse electric fields can facilitate the realization of QAH phase. Our paper not only uncovers the ferromagnetic topological properties of Bi2Te3/MnBi2Te4 bilayer tuned by electric and magnetic fields, but also can stimulate further applications to spintronics and topological devices.

关键词： Electronic structure First-principles calculations Topological materials Topological phase transition 2-dimensional systems Magnetic semiconductors Density functional theory wannier function methods

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Importance of electronic correlations in exploring the exotic phase diagram of layered LixMnO2

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Physical Review B 2023年第16期108卷 165124-165124页

作者： Hrishit Banerjee Clare P. Grey Andrew J. Morris Yusuf Hamied Department of Chemistry University of Cambridge Lensfield Road Cambridge CB2 1EW United Kingdom School of Metallurgy and Materials University of Birmingham Elms Road Edgbaston Birmingham B15 2TT United Kingdom The Faraday Institution Quad One Becquerel Avenue Harwell Campus Didcot OX11 0RA United Kingdom

Using ab initio dynamical mean-field theory we explore the electronic and magnetic states of layered LixMnO2 as a function of x, the state-of-charge. Constructing real-space wannier projections of Kohn-Sham orbitals based on the low-energy subspace of Mn 3d states and solving a multi-impurity problem, our approach focuses on local correlations at Mn sites. The antiferromagnetic insulating state in LiMnO2 has a moderate Néel temperature of TN=296K in agreement with experimental studies. Upon delithiation the system proceeds through a number of states: ferrimagnetic correlated metals at x=0.92, 0.83; multiple charge disproportionated ferromagnetic correlated metals with large quasiparticle peaks at x=0.67, 0.50, 0.33; ferromagnetic metals with small quasiparticle peaks at x=0.17, 0.08 and an antiferromagnetic insulator for the fully delithiated state, x=0.0. At moderate states of charge, x=0.67−0.33, a mix of +3/+4 formal oxidation states of Mn is observed, while the overall nominal oxidation of Mn state changes from +3 in LiMnO2 to +4 in MnO2. In all these cases the high-spin state emerges as the most likely state in our calculations considering the full d manifold of Mn based on the proximity of eg levels in energy to t2g. We observe a crossover from coherent to incoherent behavior on delithiation as function of state-of-charge.

关键词： Electronic structure Complex oxides Manganites Strongly correlated systems Transition metal oxides DFT+DMFT Dynamical mean field theory Electron-correlation calculations First-principles calculations wannier function methods

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Symmetry-conserving maximally projected wannier functions

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Physical Review B 2023年第23期107卷 235135-235135页

作者： K. Koepernik O. Janson Yan Sun J. van den Brink Institute for Theoretical Solid State Physics IFW Dresden 01069 Dresden Germany Max Planck Institute for Chemical Physics of Solids 01187 Dresden Germany Institute for Theoretical Physics and Würzburg-Dresden Cluster of Excellence ct.qmat Technische Universität Dresden 01069 Dresden Germany

To obtain a local description with a small basis size from density functional theory codes often a transformation to a local orthonormal wannier function basis is desirable. In order to do so while enforcing the constraints of the space group symmetry the symmetry conserving maximally projected wannier functions (SCMPWF) approach has been implemented in the full potential-local orbital code, FPLO. SCMPWFs are obtained from the initial step of the maximally localized wannier function algorithm, projecting a subset of wave functions onto a set of suitably chosen local trial functions with prescribed symmetry properties with subsequent orthonormalization. The particular nature of the local orbitals in FPLO makes them an ideal set of projectors since they are constructed to be a small basis adapted to the occupied sector and the lowest-lying unoccupied states. While in many cases projection onto the FPLO basis orbitals is sufficient, the option is there to choose particular local linear combinations as projectors, in order to treat cases of bond centered wannier functions. This choice turns out to lead to very localized wannier functions, which obey the space group symmetry of the crystal by construction. Furthermore we discuss the interplay of the Berry connection and position operator and especially its possible approximation, symmetries, and the optimal choice of Bloch sum phase gauge in cases where the basis is not explicitly known. We also introduce various features, which are accessible via the FPLO implementation of SCMPWFs, discuss and compare performance and provide example applications.

关键词： Electronic structure First-principles calculations Density functional theory development wannier function methods

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