论文标题
驱动手性磁铁中的阿基赛马螺钉
Archimedean Screw in Driven Chiral Magnets
论文作者
论文摘要
在手性磁铁中，磁性螺旋形成了磁化强度在传播矢量$ \ mathbf {q} $周围缠绕。从理论上讲，我们表明磁场$ \ MATHBF {b} _ {\ perp}（t）\ perp \ perp \ perp \ mathbf {q} $，它在空间上是同质的，但随着时间的推移却在振动中诱导质地周围的质地净旋转$ \ mathbf {q} $。此旋转让人联想到阿基赛螺钉的运动，等同于带有速度$ v _ {\ text {螺钉}} $平行于$ \ mathbf {q} $的翻译。由于与金石模式的耦合，这种非线性效应是针对任意弱的$ \ m athbf {b} _ {\ perp}（t）$与$ v _ {\ text {screw}} \ propto | \ mathbf | \ mathbf {b} _ {b} _ {\ perp} _ pinnning的限制。当螺旋的内部模式被激发时，并且可以通过更改$ \ Mathbf {b} _ {\ perp}（t）$来控制效果。 Archimedean螺钉可用于运输旋转和充电，因此预计螺钉运动可诱导与$ \ Mathbf {Q} $平行的电压。使用数字和浮动旋转波理论的结合，我们表明螺旋在增加$ \ mathbf {b} _ {\ perp} $增加时会变得不稳定，从而形成了``时间quasrystal''，从而在空间和时间上振荡了中等强大的驱动器。
In chiral magnets a magnetic helix forms where the magnetization winds around a propagation vector $\mathbf{q}$. We show theoretically that a magnetic field $\mathbf{B}_{\perp}(t) \perp \mathbf{q}$, which is spatially homogeneous but oscillating in time, induces a net rotation of the texture around $\mathbf{q}$. This rotation is reminiscent of the motion of an Archimedean screw and is equivalent to a translation with velocity $v_{\text{screw}}$ parallel to $\mathbf{q}$. Due to the coupling to a Goldstone mode, this non-linear effect arises for arbitrarily weak $\mathbf{B}_{\perp}(t) $ with $v_{\text{screw}} \propto |\mathbf{B}_{\perp}|^2$ as long as pinning by disorder is absent. The effect is resonantly enhanced when internal modes of the helix are excited and the sign of $v_{\text{screw}}$ can be controlled either by changing the frequency or the polarization of $\mathbf{B}_{\perp}(t)$. The Archimedean screw can be used to transport spin and charge and thus the screwing motion is predicted to induce a voltage parallel to $\mathbf{q}$. Using a combination of numerics and Floquet spin wave theory, we show that the helix becomes unstable upon increasing $\mathbf{B}_{\perp}$ forming a `time quasicrystal' which oscillates in space and time for moderately strong drive.
