Search results for "current"

Exploiting Coherence in Nonlinear Spin-Superfluid Transport

2017

We show how the interference between superfluid spin currents can endow spin circuits with coherent logic functionality. While the hydrodynamic aspects of the linear-response collective spin transport obviate interference features, we focus on the nonlinear regime, where the critical supercurrent is sensitive to the phase accumulated by the condensate in a loop geometry. We propose to control this phase by electrical gating, tuning the spin-condensate coherence length. The nonlinear aspects of the spin superfluidity thus naturally lend themselves to the construction of logic gates, uniquely exploiting the coherence of collective spin currents. Vice versa, this functionality can be used to r…

Optimal persistent currents for interacting bosons on a ring with a gauge field

2013

We study persistent currents for interacting one-dimensional bosons on a tight ring trap, subjected to a rotating barrier potential, which induces an artificial U(1) gauge field. We show that, at intermediate interactions, the persistent current response is maximal, due to a subtle interplay of effects due to the barrier, the interaction and quantum fluctuations. These results are relevant for ongoing experiments with ultracold atomic gases on mesoscopic rings.

Dynamics of noncollinear antiferromagnetic textures driven by spin current injection

2019

We present a theoretical formalism to address the dynamics of textured, noncolliear antiferromagnets subject to spin current injection. We derive sine-Gordon type equations of motion for the antiferromagnets, which are applicable to technologically important antiferromagnets such as Mn3Ir and Mn3Sn, and enables an analytical approach to domain wall dynamics in those materials. We obtain the expression for domain wall velocity, which is estimated to reach around 1 km/s in Mn3Ir by exploiting spin Hall effect with electric current density around 10^11A/m^2.

Phenomenology of current-skyrmion interactions in thin films with perpendicular magnetic anisotropy

2014

We study skyrmions in magnetic thin films with structural inversion asymmetry perpendicular to the film plane. We determine the magnetization texture of a single skyrmion and its dependence on the strength of the Dzyaloshinskii-Moriya interaction relative to the magnetostatic energy. Furthermore, we construct a phenomenological model that describes the interaction between the motion of skyrmions and electric currents to lowest order in spin-orbit coupling. We estimate the experimental verifiable velocities for current-driven motion of skyrmion textures based on available results obtained from domain walls dynamics.

Large diamagnetic persistent currents

2007

In multichannel rings, evanescent modes will always co-exist with propagating modes. The evanescent modes can carry a very large diamagnetic persistent current that can oscillate with energy and are very sensitive to impurity scattering. This provides a natural explanation for the large diamagnetic persistent currents observed in experiments.

Phenomenology of current-induced skyrmion motion in antiferromagnets

2016

We study current-driven skyrmion motion in uniaxial thin film antiferromagnets in the presence of the Dzyaloshinskii-Moriya interactions and in an external magnetic field. We phenomenologically include relaxation and current-induced torques due to both spin-orbit coupling and spatially inhomogeneous magnetic textures in the equation for the N\'eel vector of the antiferromagnet. Using the collective coordinate approach we apply the theory to a two-dimensional antiferromagnetic skyrmion and estimate the skyrmion velocity under an applied DC electric current.

Importance of the crossover-current density for a vortex-glass analysis

2000

Recent experimental results obtained from transport measurements on extremely long measurement bridges [1] have questioned the validity of previous vortex-glass analyses. For electric-field windows restricted to relatively high values of E > 10 -5 V/m the dynamic exponent of the vortex-glass transition z 6, in agreement with theoretical predictions and previous experimental results. However, for extended windows (10 -1 > E > 10 -8 V/m) - while the characteristics of a vortex-glass transition are preserved - all analyses result in z ≥ 9. A combined analysis of the crossover-current density J + 0 and crossover-electric field E + 0 , which limit the critical regime of the vortex-glass transiti…

Combined effect of magnetic field and charge current on antiferromagnetic domain-wall dynamics

2017

We theoretically examine a cross effect of magnetic field and charge current on antiferromagnetic domain wall dynamics. Since antiferromagnetic materials are largely insensitive to external magnetic fields in general, charge current has been shown recently as an alternative and efficient way to manipulate antiferromagnets. We find a new role of the magnetic field in the antiferromagnetic dynamics that appears when it is combined with charge current, demonstrating a domain wall motion in the presence of both field and current. We show that a spatially varying magnetic field can shift the current-driven domain-wall velocity, depending on the domain-wall structure and the direction of the fiel…

2017

Topological magnetic textures - like skyrmions - have become a major player in the design of next-generation magnetic storage technology due to their stability and the control of their motion by ultra-low current densities. A major challenge to develop this new skyrmion-based technology is to achieve the controlled and deterministic creation of magnetic skyrmions without the need of complex setups. We demonstrate a solution to this challenge by showing how to create skyrmions and other magnetic textures in ferromagnetic thin films by means of a homogeneous DC current and without requiring Dzyaloshinskii-Moriya interactions. This is possible by exploiting a static loss of stability arising f…

Pumping of single electrons with a traveling wave

1995

Abstract We describe the operation and performance of a one-dimensional chain of small metallic islands whose potentials are modulated in a wave-like manner. The sinusoidal voltages, applied to the gate electrodes, carry individual charges coherently through the array. In practice, the wave-like potential is induced on the gates by a surface acoustic wave (SAW) traveling on a piezoelectric substrate. The resulting transfer of charges should produce a DC current I = ± ef through the chain, where f is the frequency of the wave and the sign ofthe current depends on the value of the common DC bias of the islands as well as on the direction of the wave propagation. We observe, however, a much sm…