磁涡旋中动量向位置的转化

Topological constraints on positions of magnetic solitons in multiply-connected planar magnetic nano-elements

Here we consider an interplay between the topology of the magnetization texture (which is a topological soliton, or Skyrmion) in a planar magnetic nano-element and the topology of the element itself (its connectivity). We establish the existence of a set of constraints, coupling these topologies, which are specific for multiply connected elements and are absent in simply-connected case. As an example, a specific constraint is derived for a case of planar ring magnet, relating the angular positions of magnetic vortices and antivortices inside. We analyze the recent experimental data on the vort…

正方形排列矩形反点超导体中间隙涡旋的各向异性囚禁

Anisotropic Caging of Interstitial Vortices in Superconductors with a Square Array of Rectangular Antidots

我们研究了具有矩形亚微米孔（“反点”）的正方形阵列的超导薄膜中涡旋钉扎的各向异性。反量子点的大小是这样选择的，即它对应于饱和数n_s=1，即每个反量子点可以捕获最多一个通量量子。因此，当磁场超过第一匹配场时出现的填隙涡旋被来自饱和反点的排斥力“笼住”在填隙位置处。当平行于反点的长边测量时，我们观察到比沿着反点的短边测量的Ic（H）更高的整体临界电流Ic（H）。尽管空反点对涡旋施加的钉扎力是各向同性的，但我们的I_c（H）数据表明，间隙涡旋所经历的并由饱和反点阵列提供的束缚力是强烈各向异性的。

光学涡旋中石墨烯量子点的反常逆法拉第效应

Anomalous inverse Faraday effect for graphene quantum dots in optical vortices

本文报道了线偏振光学涡旋照射下石墨烯量子点的反常逆法拉第效应，发现离轴位置出现与涡旋波前反向旋转的磁矩，揭示轨道角动量转移效率远低于自旋，为二维系统的光学轨道角动量到磁化转换建立了新范式。

振荡囚禁玻色-爱因斯坦凝聚体中涡旋形成的观测

Observation of vortex formation in an oscillating trapped Bose-Einstein condensate

本文报道了Rb-87原子的玻色-爱因斯坦凝聚体中涡旋形成的观测结果。通过将振荡激励叠加到由外部磁场引入的捕获电势来产生涡旋。对于小振幅的外部激励场，我们观察到云轴的弯曲。增加振幅，我们观察到在样品中形成越来越多的涡流。拍摄到拍摄的变化，在凝聚云内的涡数和位置，可能是由于内在的涡旋成核动力学。我们讨论了样品中可能形成的涡旋和反涡旋以及涡旋成核的可能机制。

Band geometry from position-momentum duality at topological band crossings

We show that the position-momentum duality offers a transparent interpretation of the band geometry at the topological band crossings. Under this duality, the band geometry with Berry connection is dual to the free-electron motion under gauge field. This identifies the trace of quantum metric as the dual energy in momentum space. The band crossings with Berry defects thus induce the dual energy quantization in the trace of quantum metric. For the $\mathbb Z$ nodal-point and nodal-surface semimetals in three dimensions, the dual Landau level quantization occurs owing to the Berry charges. Meanw…

Pinning and gyration dynamics of magnetic vortices revealed by correlative Lorentz and bright-field imaging

Topological magnetic textures are of great interest in various scientific and technological fields. To allow for precise control of nanoscale magnetism, it is of great importance to understand the role of intrinsic defects in the host material. Here, we use conventional and time-resolved Lorentz microscopy to study the effect of grain size in polycrystalline permalloy films on the pinning and gyration orbits of vortex cores inside magnetic nanoislands. To assess static pinning, we use in-plane magnetic fields to shift the core across the island while recording its position. This enables us to …

Blockade of vortex flow by thermal fluctuations in atomically thin clean-limit superconductors

Resistance in superconductors arises from the motion of vortices driven by flowing supercurrents or external electromagnetic fields and may be strongly affected by thermal or quantum fluctuations. The common expectation borne out in previous experiments is that as the temperature is lowered, vortex motion is suppressed, leading to a decreased resistance. A new generation of materials provides access to the previously inaccessible regime of clean-limit superconductivity in atomically thin superconducting layers. We show experimentally that for few-layer 2H-NbSe$_2$ the resistance below the supe…

Observation of a gel of quantum vortices in a superconductor at very low magnetic fields

A gel consists of a network of particles or molecules formed for example using the sol-gel process, by which a solution transforms into a porous solid. Particles or molecules in a gel are mainly organized on a scaffold that makes up a porous system. Quantized vortices in type II superconductors mostly form spatially homogeneous ordered or amorphous solids. Here we present high-resolution imaging of the vortex lattice displaying dense vortex clusters separated by sparse or entirely vortex-free regions in $β$-Bi$_2$Pd superconductor. We find that the intervortex distance diverges upon decreasing…