The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Matthew J. W. Dodgson - One of the best experts on this subject based on the ideXlab platform.
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London Theory for superconducting phase transitions in external magnetic fields: application to UPt3.
Physical review letters, 2002Co-Authors: D. F. Agterberg, Matthew J. W. DodgsonAbstract:For multicomponent superconductors, it is known that the presence of symmetry breaking fields can lead to multiple superconducting phase transitions. Motivated by recent small angle neutron scattering experiments on the vortex state of UPt3, the London Theory in the vicinity of such phase transitions is determined. It is found that the form of this London Theory is in general quite different than that for conventional superconductors. This is due to the existence of a diverging correlation length associated with these phase transitions. One striking consequence is that nontrivial vortex lattices exist arbitrarily close to H(c1). Applications to UPt3, CeIn3, U(1-x)Th(x)Be(13), electron doped cuprate superconductors, Sr(2)RuO(4), and MgCNi(3) are discussed.
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London Theory across superconducting phase transitions: application to UPt$_3$
arXiv: Strongly Correlated Electrons, 2002Co-Authors: D. F. Agterberg, Matthew J. W. DodgsonAbstract:For multi-component superconductors, it is known that the presence of symmetry breaking fields can lead to multiple superconducting phase transitions. This phenomenon is best illustrated in UPt$_3$. Motivated by recent small angle neutron scattering experiments on the vortex state of UPt$_3$, the London Theory in the vicinity of such phase transitions is determined. It is found that the form of this London Theory is in general quite different than that for conventional superconductors. This is due to the existence of a diverging correlation length associated with these phase transitions. One striking consequence is that non-trivial vortex lattices exist arbitrarily close to H$_{c1}$. It is also found that the penetration depth develops a novel temperature dependence and anisotropy. Results of this Theory for UPt$_3$ are derived. Possible applications to CeIn$_3$, U$_{1-x}$Th$_x$Be$_{13}$, electron doped cuprate superconductors, Sr$_2$RuO$_4$, and MgCNi$_3$ are also discussed.
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Vortex collisions: crossing or recombination?
Physical review letters, 2001Co-Authors: Malek Bou-diab, Matthew J. W. Dodgson, Gianni BlatterAbstract:We investigate the collision of two vortex lines moving with viscous dynamics and driven towards each other by an applied current. Using London Theory in the approach phase we observe a nontrivial vortex conformation producing antiparallel segments; their attractive interaction triggers a violent collision. The collision region is analyzed using the time-dependent Ginzburg-Landau equation. While we find that vortices will always recombine through the exchange of segments, a crossing channel appears naturally through a double collision process.
Kazushige Machida - One of the best experts on this subject based on the ideXlab platform.
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Transverse Components of Flux Line Lattice Form Factors in Uniaxial Superconductors
Physics Procedia, 2016Co-Authors: Masanori Ichioka, Yuujirou Amano, Masahiro Ishihara, Kazushige MachidaAbstract:Abstract Magnetic field orientation dependence of transverse and longitudinal flux line lattice form factors are theoretically studied in uniaxial superconductors with extremely large anisotropy ratio 60 for some field magnitudes. The form factors are estimated by two methods, the Eilenberger Theory and the London Theory comparatively. We also compare them to the form factors observed by the small angle neutron scattering experiment on Sr2RuO4. We discuss the cutoff function of extended London Theory, and the contributions from the suppression of the pair potential as a function of the field orientation.
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Eilenberger and London theories for transverse components of flux line lattice form factors in uniaxial superconductors
Physical Review B, 2014Co-Authors: Yuujirou Amano, Masanori Ichioka, Masahiro Ishihara, N. Nakai, Kazushige MachidaAbstract:We theoretically study the magnetic field orientation dependence of longitudinal and transverse flux line lattice form factors in uniaxial superconductors with anisotropy ratio corresponding to YBa_2_Cu_3_O_{7-delta}. We discuss influences of the anisotropy ratio of coherence length, and differences between the s-wave and the d_{x^2-y^2}-wave pairings. The calculations are performed by two methods, the Eilenberger Theory and the London Theory comparatively, and we study the cutoff function of the extended London Theory, which will be helpful in the analysis of the small angle neutron scattering in the vortex states.
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Lower critical field Hc1(T) and pairing symmetry based on eilenberger Theory
Journal of the Physical Society of Japan, 2011Co-Authors: Takanobu Akiyama, Masanori Ichioka, Kazushige MachidaAbstract:We quantitatively estimate different T-dependences of Hc1 between s wave and d wave pairings by Eilenberger Theory. The T-dependences of Hc1(T) show quantitative deviation from those in London Theory. We also study differences of Hc1(T) between p+ and p- wave pairing in chiral p wave superconductors. There, Hc1(T) is lower in p- wave pairing, and shows the same T-dependence as in s wave pairing.
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Generic First Order Orientation Transition of Vortex Lattices in Type II Superconductors
Journal of the Physical Society of Japan, 2010Co-Authors: Kenta M. Suzuki, Masanori Ichioka, Kenji Inoue, Predrag Miranovic, Kazushige MachidaAbstract:First order transition of vortex lattices (VL) observed in various superconductors with four-fold symmetry is explained microscopically by quasi-classical Eilenberger Theory combined with nonlocal London Theory. This transition is intrinsic in the generic successive VL phase transition due to either gap or Fermi velocity anisotropies. This is also suggested by the electronic states around vortices. Ultimate origin of this phenomenon is attributed to some what hidden frustrations of a spontaneous symmetry broken hexagonal VL on the underlying four-fold crystalline symmetry.
C. L. Yiu - One of the best experts on this subject based on the ideXlab platform.
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The generalized Heitler–London Theory for the H3 potential energy surface
The Journal of Chemical Physics, 1999Co-Authors: U. Kleinekathöfer, K. T. Tang, J. P. Toennies, C. L. YiuAbstract:A systematic perturbation Theory has been developed to analyze the terms contributing to the H3 potential energy surface. Group Theory is used to find the irreducible representations of the Hamiltonian matrix elements which then are decoupled to their simplest level. In the case of diatomic molecules, this approach leads naturally to the Generalized Heitler–London (GHL) Theory derived previously [K. T. Tang and J. P. Toennies, J. Chem. Phys. 95, 5918 (1991)]. Many previous semi-empirical potential surfaces for the H3 triatomic system including the well known LEPS surface are examined in the light of the present results. In particular, the Cashion–Herschbach (or diatomics-in-molecules without overlap) surface is shown to encompass far more information than previously recognized. The new Theory now contains all the terms needed for an exact perturbation calculation of the potential energy surface.
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the generalized heitler London Theory for interatomic interaction and surface integral method for exchange energy
International Reviews in Physical Chemistry, 1998Co-Authors: K. T. Tang, J. P. Toennies, C. L. YiuAbstract:Based on the Theory of the permutation group and the Rayleigh-Schrodinger perturbation Theory, a systematic procedure is developed for the calculation of interatomic potentials. When this method is applied to the H molecule, the triplet (t) and singlet (s) energies are given by N N E = epsilon + s 1 epsilon, t, s n n x n = n = where epsilon and s are the n th-order polarization energy and overlap integral n n respectively, and epsilon is the exchange energy defined as epsilon = ( E - E ) 2. With N = 1, x x t s this expression is shown to be identical with the usual Heitler-London energy ; therefore this method is called generalized Heitler-London (GHL) Theory. When epsilon x is expanded in terms of the Coulomb integral and the exchange integral, many previous symmetry-adapted perturbation theories are shown to be subsets of this expansion. The advantage of the GHL Theory is that, instead of using the approximate exchange integrals, the exchange energy calculated from the surface integral method can be use...
J. P. Toennies - One of the best experts on this subject based on the ideXlab platform.
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The generalized Heitler–London Theory for the H3 potential energy surface
The Journal of Chemical Physics, 1999Co-Authors: U. Kleinekathöfer, K. T. Tang, J. P. Toennies, C. L. YiuAbstract:A systematic perturbation Theory has been developed to analyze the terms contributing to the H3 potential energy surface. Group Theory is used to find the irreducible representations of the Hamiltonian matrix elements which then are decoupled to their simplest level. In the case of diatomic molecules, this approach leads naturally to the Generalized Heitler–London (GHL) Theory derived previously [K. T. Tang and J. P. Toennies, J. Chem. Phys. 95, 5918 (1991)]. Many previous semi-empirical potential surfaces for the H3 triatomic system including the well known LEPS surface are examined in the light of the present results. In particular, the Cashion–Herschbach (or diatomics-in-molecules without overlap) surface is shown to encompass far more information than previously recognized. The new Theory now contains all the terms needed for an exact perturbation calculation of the potential energy surface.
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the generalized heitler London Theory for interatomic interaction and surface integral method for exchange energy
International Reviews in Physical Chemistry, 1998Co-Authors: K. T. Tang, J. P. Toennies, C. L. YiuAbstract:Based on the Theory of the permutation group and the Rayleigh-Schrodinger perturbation Theory, a systematic procedure is developed for the calculation of interatomic potentials. When this method is applied to the H molecule, the triplet (t) and singlet (s) energies are given by N N E = epsilon + s 1 epsilon, t, s n n x n = n = where epsilon and s are the n th-order polarization energy and overlap integral n n respectively, and epsilon is the exchange energy defined as epsilon = ( E - E ) 2. With N = 1, x x t s this expression is shown to be identical with the usual Heitler-London energy ; therefore this method is called generalized Heitler-London (GHL) Theory. When epsilon x is expanded in terms of the Coulomb integral and the exchange integral, many previous symmetry-adapted perturbation theories are shown to be subsets of this expansion. The advantage of the GHL Theory is that, instead of using the approximate exchange integrals, the exchange energy calculated from the surface integral method can be use...
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Generalized Heitler-London Theory with exchange energy by the surface integral method: an application to the alkali metal dimer cations
Chemical Physics Letters, 1996Co-Authors: Ch. Johann, K. T. Tang, Ulrich Kleinekathöfer, J. P. ToenniesAbstract:Abstract The generalized Heitler-London Theory is used to calculate the lowest gerade and ungerade potential energy curves of the alkali metal dimer cations Li 2 + , Na 2 + , K 2 + , Rb 2 + and Cs 2 + . The exchange energy is calculated with the surface integral method and the second order polarization energy by a damped induction series. The results depend only on the properties of the atomic constituents and thus the potentials of all these systems are generated by the same formula without any adjustable parameters. For Li 2 + and Na 2 + the results agree well with accurate CI calculations. The observed discrepancies for Rb 2 + and Cs 2 + with previous estimates are discussed.
Isaías G. De Oliveira - One of the best experts on this subject based on the ideXlab platform.
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Cutoff parameters in London Theory
Physical Review B, 1998Co-Authors: Isaías G. De Oliveira, A. M. ThompsonAbstract:Theory Group, Department of Physics, University of Manchester, Manchester, M13 9PL, United Kingdom~Received 21 November 1997!The exponential cutoff is used in London Theory to calculate the magnetic field inside the vortex. In thiswork, using London Theory and new numerical solutions of the conventional Ginzburg-Landau equations, weinvestigate the behavior of exponential cutoff parameter aas a function of the reduced fieldb in the wholerange of magnetic fields. We find a different behavior of this parameter for low and high magnetic fields.@S0163-1829~98!02814-8#I. INTRODUCTION
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A simple method to determine the mass parameter in uniaxial superconductors
Solid State Communications, 1997Co-Authors: Isaías G. De OliveiraAbstract:Abstract Using the anisotropic London Theory we investigate some properties of superconductors in the limit of large values of the magnetic induction. In this work we proposed a method of obtaining the average mass parameter using torque magnetometry. We consider the region where the pinning and the geometry of the sample are not important. Thus, the only relevant quantity is the angle associated to the biggest torque, θ max .
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Coexistence of orthogonal flux lines in uniaxial superconductors
Physica C-superconductivity and Its Applications, 1994Co-Authors: Mauro M. Doria, Isaías G. De OliveiraAbstract:Abstract We consider extremely type II uniaxial superconductors in the context of anistropic London Theory and study the Helmholtz free energy when the magnetic induction makes an angle of 45° with the symmetry axis. For straight vortex lines we find that the free energy is lower when the straight lines are in multiple directions, namely at θ = 0° and at 90°, instead of all oriented at 45°.
