IQIM Postdoctoral and Graduate Student Seminar

Abstract: What happens when you shine some light on a magnet? One of the first interesting things is "Goldstone mode activation", where every Goldstone mode acquires a linear velocity, . In this talk, I show how this principle can be used to build tiny machines such as nano-Archimedean screws, skyrmion jellyfish or rotating skyrmion lattices in chiral magnets. In each of these systems, the speed and direction of the Goldstone mode motion can be controlled precisely by tweaking the parameters of the drive. This invites a variety of applications: for example, the nano-Archimedean screw emerges as a powerful new transport tool, able to drive large spin or electric currents. I will briefly discuss too the emergence of "time quasicrystal" dynamics as the leading order dynamical instability when the driving power is increased.

In some systems, it turns out the direction of the motion is not purely controlled by the drive, but instead chosen spontaneously by the system itself. Such "active" motion has famously been studied in many living systems, such as flocks of birds or schools of fish. I will provide an example of how active motion can also arise in a driven magnet, specifically in a one-dimensional ferrimagnet hosting a domain wall. The driven domain wall spontaneously choses to move right or left. Amazingly, the velocity of the domain wall is not quadratic, but linear in the driving power, implying ultrafast motion at weak driving power.

Lunch will be provided, following the talk, on the lawn north of the Bridge Building.