The Experts below are selected from a list of 141768 Experts worldwide ranked by ideXlab platform
Dunghai Lee - One of the best experts on this subject based on the ideXlab platform.
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nodes in the Gap Function of lafepo the Gap Function of the fe se te systems and the stm signature of the s pairing
Physical Review B, 2010Co-Authors: Fa Wang, Hui Zhai, Dunghai LeeAbstract:We reiterate, in more details, our previous proposal of using quasi-particle 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$_{\pm}$, with nodes on electron Fermi surfaces. For Fe(Se,Te) system we found fully Gapped s$_{\pm}$ 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.
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nodes in the Gap Function of lafepo the Gap Function of the fe se te systems and the stm signature of the s pairing
APS, 2010Co-Authors: Fa Wang, Hui Zhai, Dunghai LeeAbstract:Tsinghua University (Beijing, China) ( Basic Research Young Scholars Program) and National Natural Science Foundation (China) (Grants No. 10944002 and No. 1f0847002)
P Thalmeier - One of the best experts on this subject based on the ideXlab platform.
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Gap Function of hexagonal pnictide superconductor srptas from quasiparticle interference spectrum
arXiv: Superconductivity, 2014Co-Authors: Alireza Akbari, P ThalmeierAbstract:The pnictide superconductor SrPtAs has a hexagonal layered structure containing inversion symmetry. It is formed by stacking two inequivalent PtAs layers separated by Sr layers. The former have no local (in-plane) inversion symmetry and therefore a (layer-) staggered Rashba spin orbit coupling appears which splits the three Kramers degenerate bands into six quasi-2D bands. The symmetry of the superconducting state of SrPtAs is unknown. Three candidates, spin-singlet $A_{1g}$ and $E_g$ as well as triplet $A_{2u}$ states have been proposed. We predict the quasiparticle interference (QPI) spectrum for these Gap Functions in t-matrix Born approximation. We show that distinct differences in the pattern of characteristic QPI wave vectors appear. These results may be important to determine the Gap symmetry of SrPtAs by STM-QPI method.
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Gap Function of hexagonal pnictide superconductor srptas from quasiparticle interference spectrum
EPL, 2014Co-Authors: Alireza Akbari, P ThalmeierAbstract:The pnictide superconductor SrPtAs has a hexagonal layered structure containing inversion symmetry. It is formed by stacking two inequivalent PtAs layers separated by Sr layers. The former have no local (in-plane) inversion symmetry and, therefore, a (layer-)staggered Rashba spin orbit coupling appears which splits the three Kramers degenerate bands per layer into six quasi-2D bands. The symmetry of the superconducting state of SrPtAs is unknown. Three candidates, spin-singlet and as well as triplet states have been proposed. We predict the quasiparticle interference (QPI) spectrum for these Gap Functions in t-matrix Born approximation. We show that distinct differences in the pattern of characteristic QPI wave vectors appear. These results may be important to determine the Gap symmetry of SrPtAs by STM-QPI method.
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Gap Function with point nodes in borocarbide superconductor yni2b2c
Physical Review Letters, 2002Co-Authors: K Izawa, K Kamata, Y Nakajima, Y Matsuda, Tadataka Watanabe, Minoru Nohara, Hidenori Takagi, P Thalmeier, Kazumi MakiAbstract:To determine the superconducting Gap Function of ${\mathrm{Y}\mathrm{N}\mathrm{i}}_{2}{\mathrm{B}}_{2}\mathrm{C}$, the $c$-axis thermal conductivity ${\ensuremath{\kappa}}_{zz}$ wasmeasured in $\mathbit{H}$ rotated in various directions. The angularvariation of ${\ensuremath{\kappa}}_{zz}$ in $\mathbit{H}$ rotated within the $ab$ plane shows a peculiar fourfold oscillation withnarrow cusps. The amplitude of this fourfold oscillation becomes verysmall when $\mathbit{H}$ is rotated conically around the $c$ axis with a tilt angle of 45\ifmmode^\circ\else\textdegree\fi{}. These results provide the firstcompelling evidence that the Gap Function has point nodes located along the $a$ and $b$ axes. This unprecedented Gap structure challenges the current viewon the pairing mechanism.
Xiaoqi Yang - One of the best experts on this subject based on the ideXlab platform.
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On Gap Functions for Vector Variational Inequalities
Vector Variational Inequalities and Vector Equilibria, 2000Co-Authors: Guang-ya Chen, C. J. Goh, Xiaoqi YangAbstract:We extend the theory of Gap Functions for scalar variational inequality problems (see [1,8]) to the case of vector variational inequality. The Gap Functions for vector variational inequality are defined as set-valued mappings. The significance of the Gap Function is interpreted in terms of the inverse vector variational inequality. Convexity properties of these set-valued mappings are studied under different assumptions.
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The Gap Function of a convex multicriteria optimization problem
European Journal of Operational Research, 1998Co-Authors: Guang-ya Chen, Xiaoqi YangAbstract:We generalize the concept of a Gap Function previously defined for a convex (scalar) optimization problem to a convex multicriteria optimization problem and study its various properties.
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On Gap Functions and duality of variational inequality problems
Journal of Mathematical Analysis and Applications, 1997Co-Authors: G. Y. Chen, C. J. Goh, Xiaoqi YangAbstract:Abstract We extend the definition of the Gap Function defined by Auslender for a more general class of variational inequality problems involving some convex Function. A study of the duality of the extended variational inequality problem and its dual sheds new light on the meaning of Gap Functions. Convexity and differentiability of the Gap Function are also studied and sufficient conditions are derived. We also show how the Gap Functions for the primal and the dual are related by dual Fenchel optimization problems.
Anthony Chen - One of the best experts on this subject based on the ideXlab platform.
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Reformulating Environmentally Constrained Traffic Equilibrium via a Smooth Gap Function
International Journal of Sustainable Transportation, 2015Co-Authors: Anthony Chen, Lin ChengAbstract:Various government laws have recently been enacted to alleviate the environmental deterioration of transportation systems. Environmental constraint is a valid means to explicitly reflect various environmental protection requirements imposed by the government. In this paper, we examine the environmentally constrained traffic equilibrium problem (EC-TEP), which is a fundamental tool for modeling and evaluating environmental protection requirements. Specifically, we provide an equivalent reformulation for the EC-TEP. The proposed reformulation adapts the concept of Gap Function to simultaneously reformulate the nonlinear complementarity conditions associated with the generalized user equilibrium conditions, environmental constraints, and conservation constraints as an equivalent unconstrained optimization problem. This Gap Function reformulation has two desirable features: (1) it can handle a general environmental constraint structure (linear or nonlinear; link-based or area-based) and a general link and rou...
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reformulating the traffic equilibrium problem via a smooth Gap Function
Mathematical and Computer Modelling, 2000Co-Authors: Anthony ChenAbstract:This paper proposes an alternate formulation of the traffic assignment problem using route flows and the shortest Origin-Destination (OD) travel times as the decision variables. This is accomplished through defining a Gap Function to convert the Nonlinear Complementarity Problem (NCP) formulation to an equivalent Mathematical Program (MP). This formulation has two advantages: 1.(i) it can model assignment problems with general route costs which cannot be accomplished with existing formulations that use link-flow variables 2.(ii) the objective Function is smooth, convex, and bounded, which permits efficient MP algorithms for its solution. Two solution approaches are developed to solve the proposed formulation. The first is based on a set of working routes, which are modeled as ''known a priori'' based on travelers' preferences or interviews. The second approach uses a column generation procedure to generate a new route in each iteration on a need basis. For each approach, we use a Successive Quadratic Programming (SQP) algorithm to solve for the solutions. To show that the formulation is correct, we solve a small example with a general route cost and compare it to the classic traffic equilibrium problem which assumes an additive route cost Function. Finally, numerical results for a medium-sized network are provided to demonstrate the feasibility of the solution approach.
Y Maeno - One of the best experts on this subject based on the ideXlab platform.
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ultrasound attenuation in sr 2 ruo 4 an angle resolved study of the superconducting Gap Function
Physical Review Letters, 2001Co-Authors: Christian Lupien, Zhiqiang Mao, W A Macfarlane, Cyril Proust, Louis Taillefer, Y MaenoAbstract:We present a study of the electronic ultrasound attenuation alpha in the unconventional superconductor Sr(2)RuO(4). The power law behavior of alpha at temperatures down to T(c)/30 clearly indicates the presence of nodes in the Gap. In the normal state, we find an enormous anisotropy of alpha in the basal plane of the tetragonal structure. In the superconducting state, the temperature dependence of alpha also exhibits significant anisotropy. We discuss these results in relation to possible Gap Functions.
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temperature dependence of the penetration depth in sr2ruo4 evidence for nodes in the Gap Function
Physical Review Letters, 2000Co-Authors: I J Bonalde, Brian David Yanoff, M B Salamon, D J Van Harlingen, E M E Chia, Zhiqiang Mao, Y MaenoAbstract:We report measurements of the magnetic penetration depth in single crystals of ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$ down to 0.04 K using a tunnel-diode based, self-inductive technique. We observe a power law temperature dependence below 0.8 K, with no sign of a second phase transition nor of a crossover predicted for a multiband superconductor. A power law dependence suggests that the Gap Function has nodes, inconsistent with candidate $p$-wave states. We argue that nonlocal effects, rather than impurity scattering, can explain the observed ${T}^{2}$ dependence instead of the $T$-linear behavior expected for line nodes.
