Manipulation of magnetic skyrmions by superconducting vortices in ferromagnet-superconductor heterostructures

Abstract

Dynamics of magnetic skyrmions in hybrid ferromagnetic films harbors novel physical phenomena and holds promise for technological applications. In this work, we discuss the behavior of magnetic skyrmions when coupled to superconducting vortices in a ferromagnet-superconductor heterostructure. We use numerical simulations and analytic arguments to reveal broader possibilities for manipulating the skyrmion-vortex dynamic correlations in the hybrid system, that are not possible in its separated constituents. We explore the thresholds of particular dynamic phases, and quantify the phase diagram as a function of the relevant material parameters, applied current and induced magnetic torques. Finally, we demonstrate the broad and precise tunability of the skyrmion Hallangle in presence of vortices, with respect to currents applied to either or both the superconductor and the ferromagnet within the heterostructure.

Chiral edge currents for ac-driven skyrmions in confined pinning geometries

“…In the absence of quenched disorder or pinning, the skyrmion Hall angle is constant; however, when quenched disorder is present, the skyrmion Hall angle becomes drive or velocity dependent, starting at a value of nearly zero just above the depinning threshold and approaching the disorder-free limit at higher drives [41][42][43][44][45][46][47][48]. The Magnus force also causes the skyrmions to exhibit cyclotron or spiraling motion when they are in a confining potential or interacting with a pinning site [41,[49][50][51][52][53][54][55][56]. Skyrmions can perform circular orbits under biharmonic drives [57], oscillating fields [58,59], and in certain types of driven bilayer systems [60].…”

Mesoscale phase separation of skyrmion-vortex matter in chiral magnet-superconductor heterostructures

“…Recently, there has been an increasing interest on the hybridization of topologically-protected magnetic textures called skyrmions and Abrikosov vortices in heterostructures comprising a superconducting (SC) film and a chiral magnetic (CM) layer [20][21][22][23][24][25][26]. In these systems, a skyrmion and a nearby vortex interact with each other via their stray fields and/or via spin-orbit coupling (SOC) between the SC and CM layers.…”

“…In these systems, a skyrmion and a nearby vortex interact with each other via their stray fields and/or via spin-orbit coupling (SOC) between the SC and CM layers. In the case of attractive interaction, they eventually form a bound pair with easily tunable dynamical properties [20][21][22][23]. In particular, for strong SOC, a skyrmion-vortex pair can host localized Majorana bound states, which makes SC-CM hybrids a promising platform for future applications in topological quantum computing [24,26,27].…”

“…Finally, we model the electromagnetic coupling between a vortex and a skyrmion by V vs (r) = vs /(1 + r 2 /λ 2 vs ) 2 , where vs can be either negative or positive, depending on whether the skyrmion is oriented parallel or antiparallel to the vortex, and λ vs 0.8λ (see Ref. [23] and the Supplemental Material [48]). For d I = 0, this potential could also represent qualitatively the effect of proximity induced SOC between the SC and CM layers [20,22].…”

“…where η v (η s ) is the vortex (skyrmion) viscous drag coefficient and G = G ẑ is the gyromagnetic vector [23]. The Gaussian noises γ vi (t) and γ si (t) satisfy γ µ αi (t) = 0 and vs , ns0 = 3.77λ −2 vs , and ξs = 0.5λvs, featuring the homogeneous phase (H) and six distinct microphases: bubbles (B), stripes (S), clusters (C), vortex-filled skyrmion bubbles (SkB), intercalated stripes (IS), and skyrmion-filled vortex bubbles (VB).…”