We study the quantum mechanics of magnetic skyrmions in the vicinity of the skyrmion-crystal to ferromagnet phase boundary in two-dimensional magnets. We show that the skyrmion excitation has an energy dispersion that splits into multiple bands due to the combination of magnus force and the underlying lattice. Condensation of the skyrmions can give rise to an intermediate phase between the skyrmion crystal and ferromagnet: a quantum liquid, in which skyrmions are not spatially localized. We show that the critical behavior depends on the spin size $S$ and the topological number of the skyrmion. Experimental signatures of quantum skyrmions in inelastic neutron-scattering measurements are also discussed.
We report experimental coupling of chiral magnetism and superconductivity in [IrFeCoPt]/Nb heterostructures. The stray field of skyrmions with radius ~50nm is sufficient to nucleate antivortices in a 25nm Nb film, with unique signatures in the magnetization, critical current and flux dynamics, corroborated via simulations. We also detect a thermally-tunable Rashba-Edelstein exchange coupling in the isolated skyrmion phase. This realization of a strongly interacting skyrmion-(anti)vortex system opens a path towards controllable topological hybrid materials, unattainable to date.
We present a novel approach to understanding the extraordinary diversity of magnetic skyrmion solutions. Our approach combines a new classification scheme with efficient analytical and numerical methods. We introduce the concept of chiral kinks to account for regions of disfavoured chirality in spin textures, and classify two-dimensional magnetic skyrmions in terms of closed domain walls carrying such chiral kinks. In particular, we show that the topological charge of magnetic skyrmions can be expressed in terms of the constituent closed domain walls and chiral kinks. Guided by our classificat…
Chiral Magnetic Skyrmions with Arbitrary Topological Charge ("skyrmionic sacks")
我们表明，连续和自旋晶格模型的手征铁磁和反铁磁提供了一个无限多个稳定的孤子解的任何整数拓扑电荷的存在。新skyrmions的形态和相应的能量依赖性的详细描述。所考虑的模型是通用的，并且预期预测可能发生在包括原子层的各种手性磁体中的过多的粒子状状态，例如，PdFe/Ir（111）、菱形GaV $_4$ S $_8$半导体、B20型合金如Mn $_{1-x}$ Fe $_x$ Ge、Mn $_{1-x}$ Fe $_x$ Si、Fe $_{1-x}$ Co $_x$ Si、Cu $_2$ OSeO $_3$、无中心四元Heusler化合物。
Synthesis of new materials that can host magnetic skyrmions and their thorough experimental and theoretical characterization are essential for future technological applications. The $β$-Mn-type compound FePtMo$_3$N is one such novel material that belongs to the chiral space group $P4_132$, where the antisymmetric Dzyaloshinkii-Moriya interaction is allowed due to the absence of inversion symmetry. We report the results of small-angle neutron scattering (SANS) measurements of FePtMo$_3$N and demonstrate that its magnetic ground state is a long-period spin helix with a Curie temperature of 222~K…
Magnetic skyrmions are vortex-like topological spin textures often observed in structurally chiral magnets with Dzyaloshinskii-Moriya interaction. Among them, Co-Zn-Mn alloys with a $β$-Mn-type chiral structure host skyrmions above room temperature. In this system, it has recently been found that skyrmions persist over a wide temperature and magnetic field region as a long-lived metastable state, and that the skyrmion lattice transforms from a triangular lattice to a square one. To obtain perspective on chiral magnetism in Co-Zn-Mn alloys and clarify how various properties related to the skyrm…
In a $β$-Mn-type chiral magnet Co$_9$Zn$_9$Mn$_2$, we demonstrate that the magnetic field-driven collapse of a room temperature metastable topological skyrmion lattice passes through a regime described by a partial topological charge inversion. Using Lorentz transmission electron microscopy, the magnetization distribution was observed directly as the magnetic field was swept antiparallel to the original skyrmion core magnetization, i.e. negative magnetic fields. Due to the topological stability of skyrmions, a direct transition of the metastable skyrmion lattice to the equilibrium helical stat…
Onset of a skyrmion phase by chemical substitution in MnGe chiral magnet
用中子小角散射方法研究了含$x$（$0 \leq x \leq 0.3$）的Mn $_{1-x}$ Fe $_{x}$ Ge合金的磁相图的演化。我们毫不含糊地观察到的skyrmion晶格（或A-相）在散装MnGe和其发病下一个小的Mn/Fe替代的情况下。在那里，A相被赋予特殊的skyrmion密度，并且在非常大的温度区域和与Fe浓度成比例的场范围内稳定。我们的研究结果强调了通过化学掺杂来微调Skyrmion晶格特性的可能性。
Skyrmions are of interest both from a fundamental and technological point of view, due to their potential to act as information carriers. But one challenge concerns their manipulation, especially at high temperature where thermal fluctuations eventually disintegrate them. Here we study the competition between skyrmions and a chiral spin liquid, using the latter as an entropic buffer to impose a quasi-vacuum of skyrmions. As a result, the temperature becomes a knob to tune the skyrmion density from a dense liquid to a diluted gas, protecting the integrity of each skyrmion from paramagnetic disi…
We investigate theoretically the equilibrium configurations of many magnetic skyrmions interacting with many superconducting vortices in a superconductor-chiral magnet bilayer. We show that miscible mixtures of vortices and skyrmions in this system breaks down at a particular wave number for sufficiently strong coupling, giving place to remarkably diverse mesoscale patterns: gel, stripes, clusters, intercalated stripes and composite gel-cluster structures. We also demonstrate that, by appropriate choice of parameters, one can thermally tune between the homogeneous and density-modulated phases.
Magnetic materials can host skyrmions, which are topologically non-trivial spin textures. In chiral magnets with cubic lattice symmetry, all previously-observed skyrmion phases require thermal fluctuations to become thermodynamically stable in bulk materials, and therefore exist only at relatively high temperature, close to the helimagnetic transition temperature. Other stabilization mechanisms require a lowering of the cubic crystal symmetry. Here, we report the identification of a second skyrmion phase in Cu$_{2}$OSeO$_{3}$ at low temperature and in the presence of an applied magnetic field.…
Chiral skyrmionic superconductivity from doping a Chern Ferromagnet
Princeton Center for Theoretical Science, Princeton University（普林斯顿大学理论物理中心）；Department of Physics and National High Magnetic Field Laboratory, Florida State University（佛罗里达州立大学物理系及国家高磁场实验室）；Theoretical Division, T-4 and CNLS, Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室理论部T-4和CNLS）；Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室集成纳米技术中心）
