1,721,110 research outputs found
Li dai di wang fa tie.
No full textCaption title.; 880-05 Title varies: Di yi. Li dai di wang fa tie -- Di er-di si. Li dai ming chen fa tie -- Wu. Zhu jia gu fa tie -- Di liu-di shi. Fa tie.; Special collection from London Missionary Society.; Oriental style, in case.; Inscriptions on stone.; Also available in an electronic version via the Internet at http://nla.gov.au/nla.gen-vn1918644.880-02 Li dai ming chen fa tie.880-03 Zhu jia gu fa tie.880-04 Fa tie
Realization of the exactly solvable Kitaev honeycomb lattice model in a spin-rotation-invariant system
No full textThe exactly solvable Kitaev honeycomb lattice model is realized as the low-energy effect Hamiltonian of a spin-1/2 model with spin rotation and time-reversal symmetry. The mapping to low-energy effective Hamiltonian is exact without truncation errors in traditional perturbation series expansions. This model consists of a honeycomb lattice of clusters of four spin-1/2 moments and contains short-range interactions up to six-spin (or eight-spin) terms. The spin in the Kitaev model is represented not as these spin-1/2 moments but as pseudospin of the two-dimensional spin-singlet sector of the four antiferromagnetically coupled spin-1/2 moments within each cluster. Spin correlations in the Kitaev model are mapped to dimer correlations or spin-chirality correlations in this model. This exact construction is quite general and can be used to make other interesting spin-1/2 models from spin-rotation invariant Hamiltonians. We discuss two possible routes to generate the high-order spin interactions from more natural couplings, which involves perturbative expansions thus breaks the exact mapping, although in a controlled manner
Schwinger boson mean field theories of spin liquid states on a honeycomb lattice: Projective symmetry group analysis and critical field theory
No full textMotivated by the recent numerical evidence [Z. Meng, T. Lang, S. Wessel, F. Assaad, and A. Muramatsu, Nature (London) 464, 847 (2010)] of a short-range resonating valence bond state in the honeycomb lattice Hubbard model, we consider Schwinger boson mean field theories of possible spin liquid states on honeycomb lattice. From general stability considerations the possible spin liquids will have gapped spinons coupled to Z(subscript 2) gauge field. We apply the projective symmetry group method to classify possible Z2 spin liquid states within this formalism on honeycomb lattice. It is found that there are only two relevant Z(subscript 2) states, differed by the value of gauge flux, zero or π, in the elementary hexagon. The zero-flux state is a promising candidate for the observed spin liquid and continuous phase transition into commensurate Néel order. We also derive the critical field theory for this transition, which is the well-studied O(4) invariant theory [A. V. Chubukov, T. Senthil, and S. Sachdev, Phys. Rev. Lett. 72, 2089 (1994); A. V. Chubukov, S. Sachdev, and T. Senthil, Nucl. Phys. B 426, 601 (1994); S. V. Isakov, T. Senthil, and Y. B. Kim, Phys. Rev. B 72, 174417 (2005)], and has an irrelevant coupling between Higgs and boson fields with cubic power of spatial derivatives as required by lattice symmetry. This is in sharp contrast to the conventional theory [S. Sachdev and N. Read, Int. J. Mod. Phys. B 5, 219 (1991)], where such transition generically leads to incommensurate magnetic order. In this scenario the Z2 spin liquid could be close to a tricritical point. Soft boson modes will exist at seven different wave vectors. This will show up as low-frequency dynamical spin susceptibility peaks not only at the Γ point (the Néel order wave vector) but also at Brillouin-zone-edge center M points and twelve other points. Some simple properties of the π-flux state are studied as well. Symmetry allowed further neighbor mean field ansatz are derived in appendices which can be used in future theoretical works along this direction
Topological relation between bulk gap nodes and surface bound states: Application to iron-based superconductors
No full textIn the past few years materials with protected gapless surface (edge) states have risen to the central stage of condensed matter physics. Almost all discussions centered around topological insulators and superconductors, which possess full quasiparticle gaps in the bulk. In this paper we argue that systems with topological stable bulk nodes offer another class of materials with robust gapless surface states. Moreover the location of the bulk nodes determines the Miller index of the surfaces that show (or do not show) such states. Measuring the spectroscopic signature of these zero modes allows a phase-sensitive determination of the nodal structures of unconventional superconductors when other phase-sensitive techniques are not applicable. We apply this idea to gapless iron-based superconductors and show how to distinguish accidental from symmetry-dictated nodes. We shall argue that the same idea leads to a method for detecting a class of the elusive spin liquids
Heterophyton, a new substitute name for Allophyton X.W. Wu (Pteridopsida)
Full text linkWang, Fa-Guo, Xing, Fu-Wu (2014): Heterophyton, a new substitute name for Allophyton X.W. Wu (Pteridopsida). Phytotaxa 163 (5): 299-300, DOI: 10.11646/phytotaxa.163.5.6, URL: http://dx.doi.org/10.11646/phytotaxa.163.5.
Two new and one newly recorded species of Anomala Samouelle, 1819 (Coleoptera Scarabaeidae: Rutelinae) from Yunnan, China
No full textHuang, Gui-Qiang, Wang, Fa-Lei (2019): Two new and one newly recorded species of Anomala Samouelle, 1819 (Coleoptera Scarabaeidae: Rutelinae) from Yunnan, China. Zootaxa 4706 (2): 366-374, DOI: 10.11646/zootaxa.4706.2.
Nodes in the gap function of LaFePO, the gap function of the Fe(Se,Te) systems, and the STM signature of the s(+/-) pairing
No full textWe reiterate, in more details, our previous proposal of using quasiparticle interference to determine the pairing form factor in iron-based superconductors. We also present our functional renormalization group (FRG) results on LaFePO and Fe(Se,Te) superconductors. In particular, we found that the leading pairing channel in LaFePO is nodal s± with nodes on electron Fermi surfaces. For Fe(Se,Te) system we found fully gapped s± pairing with substantial gap anisotropy on electron Fermi surfaces and large gap is concentrated in regions with dominant xy orbital character. We further fit the form factor obtained by FRG to real-space orbital basis pairing picture, which shows more clearly the differences between different iron-based superconductors.Tsinghua University (Beijing, China) ( Basic Research Young Scholars Program) and National Natural Science Foundation (China) (Grants No. 10944002 and No. 1f0847002)United States. Dept. of Energy (Grant No. DE-AC02-05CH11231
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Nearly flat band with Chern number C=2 on the dice lattice
No full textMotivated by recent experiments on the material Ba[subscript 3]NiSb[subscript 2]O[subscript 9], we consider a spin-one quantum antiferromagnet on a triangular lattice with the Heisenberg bilinear and biquadratic exchange interactions and a single-ion anisotropy. Using a fermionic “triplon” representation for spins, we study the phase diagram within mean-field theory. In addition to a fully gapped spin-liquid ground state, we find a state where one gapless triplon mode with a Fermi surface coexists with d+id topological pairing of the other triplons. Despite the existence of a Fermi surface, this ground state has fully gapped bulk spin excitations. Such a state has linear in-temperature specific heat and constant in-plane spin susceptibility, with an unusually high Wilson ratio.Boston Colleg
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