Speaker
Description
I will present work that investigates the dynamics of quantized vortices in superfluid $^4$He confined to nanoscale geometries, where vortex motion is strongly influenced by pinning on disordered substrate surfaces. We present a numerical model for quasi-2D geometries that captures vortex-surface interactions as a velocity-dependent mutual friction; results from our numerical simulations show good agreement with experimental observations of decaying 2D turbulence in 500 nm vertical confinement. To further probe these dynamics, we introduce a high-sensitivity electromechanical setup—a nanofluidic Helmholtz resonator parametrically coupled to an RF LC circuit. By leveraging dynamical backaction to enhance the dissipation sensitivity of fourth-sound modes, we achieve vortex detection in 900 nm channels at relatively short timescales allowing the study of the vortex dynamics. Experimental studies of vortex states created by external rotation reveal evidence of vorticity avalanches and a significant dependence on system history, providing new insights into the complex interplay between vortex pinning and fluid flow in confined superfluids.