6,366 research outputs found
Mass-driven vortex collisions in flat superfluids
Quantum vortices are often endowed with an effective inertial mass, due, for example, to massive particles in their cores. Such âmassive vorticesâ display new phenomena beyond the standard picture of superfluid vortex dynamics, where mass is neglected. In this work, we demonstrate that massive vortices are allowed to collide, as opposed to their massless counterparts. We propose a scheme to generate controllable, repeatable, deterministic collisional events in pairs of quantum vortices. We demonstrate two mass-driven fundamental processes: (i) the annihilation of two counter-rotating vortices and (ii) the merging of two corotating vortices, thus pointing out new mechanisms supporting incompressible-to-compressible kinetic-energy conversion, as well as doubly quantized vortex stabilization in flat superfluids
The key role of off-axis singularities in free-space vortex transmutation
We experimentally demonstrate the generation of off-axis phase singularities
in a vortex transmutation process induced by the breaking of rotational
symmetry. The process takes place in free space by launching a highly-charged
vortex, owning full rotational symmetry, into a linear thin diffractive element
presenting discrete rotational symmetry. It is shown that off-axis phase
singularities follow straight dark rays bifurcating from the symmetry axis.
This phenomenon may provide new routes towards the spatial control of multiple
phase singularities for applications in atom trapping and particle
manipulation.Comment: 4 pages, 4 figures, to appear in Applied Physics B: Lasers and Optic
Field-free nucleation of antivortices and giant vortices in non-superconducting materials
Giant vortices with higher phase-winding than are usually
energetically unfavorable, but geometric symmetry constraints on a
superconductor in a magnetic field are known to stabilize such objects. Here,
we show via microscopic calculations that giant vortices can appear in
intrinsically non-superconducting materials, even without any applied magnetic
field. The enabling mechanism is the proximity effect to a host superconductor
where a current flows, and we also demonstrate that antivortices can appear in
this setup. Our results open the possibility to study electrically controllable
topological defects in unusual environments, which do not have to be exposed to
magnetic fields or intrinsically superconducting, but instead display other
types of order.Comment: Revised version; 4 pages manuscript, 4 pages supplemental, 6 figure
Dynamics of two coupled vortices in a spin valve nanopillar excited by spin transfer torque
We investigate the dynamics of two coupled vortices driven by spin transfer.
We are able to independently control with current and perpendicular field, and
to detect, the respective chiralities and polarities of the two vortices. For
current densities above , a highly coherent signal
(linewidth down to 46 kHz) can be observed, with a strong dependence on the
relative polarities of the vortices. It demonstrates the interest of using
coupled dynamics in order to increase the coherence of the microwave signal.
Emissions exhibit a linear frequency evolution with perpendicular field, with
coherence conserved even at zero magnetic field
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