Dynamic Properties Of Vortices Research Articles

Systems of Vortices in a Binary Core–Shell Bose–Einstein Condensate

A trapped Bose--Einstein-condensed mixture of two types of cold atoms with significantly different masses has been simulated numerically within the coupled Gross--Pitaevskii equations. A configuration consisting of a vortex-free core and a shell penetrated by quantum vortices is possible in the phase separation regime. The dynamic properties of vortices in the shell are determined by several parameters. Physically implementable parametric domains corresponding to long-lived strongly nonstationary systems of several vortices attached to the core have been sought. A number of realistic numerical examples of three vortex pairs existing for many hundreds of characteristic times have been presented.

Vortex pairs in a spin-orbit-coupled Bose-Einstein condensate

Static and dynamic properties of vortices in a two-component Bose-Einstein condensate with Rashba spin-orbit coupling are investigated. The mass current around a vortex core in the plane-wave phase is found to be deformed by the spin-orbit coupling, and this makes the dynamics of the vortex pairs quite different from those in a scalar Bose-Einstein condensate. The velocity of a vortex-antivortex pair is much smaller than that without spin-orbit coupling, and there exist stationary states. Two vortices with the same circulation move away from each other or unite to form a stationary state.

Vortex Properties of Nanosized Superconducting Strips with One Central Weak Link Under an Applied Current Drive

The static and dynamic properties of vortices in a nanosized superconducting strip with one central weak link (weakly superconducting region or normal metal) are investigated in the presence of external magnetic and electric fields. The time-dependent Ginzburg–Landau equations are used to describe the electronic transport and have been solved numerically by a finite element analysis. Anisotropy is included through the spatially dependent anisotropy coefficient \(\zeta \) in different layers of the sample. Our results show that the energy barrier for vortices to enter a weak link is smaller than that for vortices to enter the superconducting layers. The magnetization shows periodic oscillations. With the introduction of the weak link, the period of oscillations decreases.

Anisotropy in the Transport Properties of Type II Superconducting Films with Periodic Pinning

Using numerical simulations, we analyze the anisotropy effects in the critical currents and dynamical properties of vortices in a thin superconducting film submitted to hexagonal and Kagome periodical pinning arrays. The calculations are performed at zero temperature, for transport currents parallel and perpendicular to the main axis of the lattice, and parallel to the diagonal axis of the rhombic unit cell. We show that the critical currents and dynamic properties are anisotropic for both pinning arrays and all directions of the transport current. The anisotropic effects are more significant just above the critical current and disappear with higher values of current and both pinning arrays. The dynamical phases for each case and a wide range of transport forces are analyzed.

Static and dynamic properties of vortices in anisotropic magnetic disks

We investigate the effect of the magnetic anisotropy (Kz) on the static and dynamic properties of magnetic vortices in small disks. Our micromagnetic calculations reveal that for a range of Kz there is an enlargement of the vortex core. We analyze the influence of Kz on the dynamics of the vortex core magnetization reversal under the excitation of a pulsed field. The presence of Kz, which lead to better resolved vortex structures, allows us to discuss in more details the role played by the in-plane and perpendicular components of the gyrotropic field during the vortex-antivortex nucleation and annihilation.

Dynamical Properties of Vortices in a Bose-Einstein Condensate in a Rotating Lattice

We present simulation results of the vortex dynamics in a trapped Bose-Einstein condensate in the presence of a rotating optical lattice. Changing the potential amplitude and the relative rotation frequency between the condensate and the optical lattice, we find a rich variety of dynamical phases of vortices. In particular, when the optical lattice rotates faster than the condensate, the competition between the pinning force and the interactions by nucleated interstitial vortices leads to the melting of vortex lattice, yielding a vortex liquid phase.

Relaxation schemes for normal modes of magnetic vortices: Application to the scattering matrix

Relaxation schemes for finding normal modes of nonlinear excitations are described and applied to the vortex-spinwave scattering problem in classical two-dimensional easy-plane Heisenberg models. The schemes employ the square of an effective Hamiltonian to ensure positive eigenvalues, together with an evolution in time or a self-consistent Gauss-Seidel iteration producing diffusive relaxation. We find some of the lowest frequency spinwave modes in a circular system with a single vortex present. The method is used to describe the vortex-spinwave scattering $(S$-matrix and phase shifts) and other dynamical properties of vortices in ferromagnets and antiferromagnets, for systems larger than that solvable by diagonalization methods. The lowest frequency modes associated with translation of the vortex center are used to estimate the vortex mass.

Static and dynamic properties of vortices in a small Josephson-junction array

An array consisting of 12 junctions arranged in a triangular lattice has recently been observed to exhibit quantum interference of vortices. That vortices should exist in such small arrays and exhibit classical behavior qualitatively similar to those found in larger arrays has been an important assumption for the interpretation of experimental results. We therefore investigate, using static and dynamic simulations, the classical properties of vortices in a small Josephson-junction array. By employing a relaxation technique, we find that the energy barrier, U b , preventing a single vortex from moving from the center of one array-lattice site to the next is dependent on the applied frustration ƒ, where ƒ is the number of flux quanta per unit cell. Solving the set of coupled-second order differential equations derived from the RCSJ model, we observe for f≥0.08 a vortex-flow region in the array's I-V characteristic.

Magnetic Flux-Line Lattices and Vortices in the Copper Oxide Superconductors

A variety of recent experiments on both the static and the dynamic properties of vortices and flux-line lattices in the mixed state of the copper oxide superconductors are discussed. The experiments are of two basic types: (i) experiments that image the magnetic flux patterns either with magnetic decoration or neutrons and give information about static structures, and (ii) experiments that explore the dynamics of vortices either through the resistivity or other electrodynamic responses of the material. Results of these experiments argue in favor of the existence of a true phase transition in the high-field vortex state from a low-temperature superconducting vortex glass phase into a disordered high-temperature vortex fluid phase. The vortex glass phase transition model does a good job of explaining high-precision measurements of the dynamics at the transition. At low fields and temperatures, very long range hexatic order in the flux-line lattice is observed.