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Airdrie, Canada

Lipavsky P.,Charles University | Kolacek J.,ASCR Institute of Physics Prague | Lin P.-J.,Universal Analytics Inc
Physica C: Superconductivity and its Applications | Year: 2016

We formulate a theory based on the time-dependent Ginzburg-Landau (TDGL) theory and Newtonian vortex dynamics to study the transverse acousto-electric response of a type-II superconductor with Abrikosov vortex lattice. When exposed to a transverse acoustic wave, Cooper pairs emerge from the moving atomic lattice and moving electrons. As in the Tolman-Stewart effect in a normal metal, an electromagnetic field is radiated from the superconductor. We adapt the equilibrium-based TDGL theory to this non-equilibrium system by using a floating condensation kernel. Due to the interaction between normal and superconducting components, the radiated electric field as a function of magnetic field attains a maximum value occurring below the upper critical magnetic field. This local increase in electric field has weak temperature dependence and is suppressed by the presence of impurities in the superconductor. © 2016 Elsevier B.V. All rights reserved.

Hari Dass N.D.,Chennai Mathematical Institute | Peter Matlock,Universal Analytics Inc
Indian Journal of Physics | Year: 2014

A covariant calculus for the construction of effective string theories is developed. Effective string theory, describing quantum string-like excitations in arbitrary dimension, has in the past been constructed using the principles of conformal field theory, but not in a systematic way. Using the freedom of choice of field definition, a particular field definition is made in a systematic way to allow an explicit construction of effective string theories with manifest exact conformal symmetry. The impossibility of a manifestly invariant description of the Polchinski-Strominger Lagrangian is demonstrated and its meaning is explained. © 2014 Indian Association for the Cultivation of Science.

Chen Y.-J.,National Chiao Tung University | Lin P.J.,Universal Analytics Inc | Wu K.H.,National Chiao Tung University | Rosenstein B.,National Chiao Tung University | And 3 more authors.
Superconductor Science and Technology | Year: 2013

The comprehensive ρ(T) measurements and the consequent resistivity curvature mapping (RCM) on Y0.7Ca0.3Ba2Cu 3O7-δ thin films (doping levels p = 0.08-0.21) elucidate a phase diagram for the whole doping range. This phase diagram further strengthens a view that the 'normal' phase in hole-doped cuprates should be divided into a strong superconducting (SC) fluctuation phase and the 'real' normal phase in which there is no significant influence of SC. The temperature of superconducting fluctuations Tf as a function of p was calculated using the Ginzburg-Landau model for layered superconductors. Comparisons between Tf and the Nernst temperature establish the origin of the Nernst effect as SC fluctuations. Some of the details in ρ(T) cannot be fully understood by the existing models and call for a more sophisticated theory of carrier dynamics in cuprates. © 2013 IOP Publishing Ltd.

Sopik B.,Charles University | Sopik B.,ASCR Institute of Physics Prague | Lipavsky P.,Charles University | Lipavsky P.,ASCR Institute of Physics Prague | And 5 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

Using principles of the Fadeev-Lovelace-Watson multiple scattering expansion, a T-matrix approximation is derived which coincides with the Galitskii-Feynman T matrix in the normal state and yields the gap in the superconducting state. Unlike other T-matrix approaches, the theory satisfies not only the self-consistent Thouless criterion but also the Baym-Kadanoff conditions for a conserving theory in equilibrium. In single-mode approximation it simplifies to the Eliashberg theory. © 2011 American Physical Society.

Lipavsky P.,Charles University | Elmurodov A.,Charles University | Lin P.-J.,Old Dominion University | Matlock P.,Universal Analytics Inc | Berdiyorov G.R.,University of Antwerp
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Within the time-dependent Ginzburg-Landau theory we discuss the effect of nonmagnetic interactions between the normal current and supercurrent in the presence of electric and magnetic fields. The correction due to the current-current interactions is shown to have a transient character so that it contributes only when a system evolves. Numerical studies for thin current-carrying superconducting strips with no magnetic feedback show that the effect of the normal current corrections is more pronounced in the resistive state where fast-moving kinematic vortices are formed. Simulations also reveal that the largest contribution due to current-current interactions appears near the sample edges, where the vortices reach their maximal velocity. © 2012 American Physical Society.

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