Visualization of quantized vortex reconnection enabled by laser ablation.

Impurity injection into superfluid helium is a simple and appealing method with diverse applications, including high-precision spectroscopy, quantum computing with surface electrons, nano/micromaterial synthesis, and flow visualization. Quantized vortices play a major role in the interaction between superfluid helium and light impurities. However, the basic principle governing this interaction is still unclear for dense (high mass density and refractive index) materials, such as semiconductor and metal impurities. Here, we provide experimental evidence of the dense silicon nanoparticle attraction to the quantized vortex cores. We prepared the silicon nanoparticles via in situ laser ablation. Following laser ablation, we observed that the silicon nanoparticles formed curved filament-like structures, indicative of quantized vortex cores. We also observed that two accidentally intersecting quantized vortices exchanged their parts, a phenomenon called quantized vortex reconnection. This behavior closely matches the dynamical scaling of reconnections. Our results provide a previously unexplored method for visualizing and studying impurity-quantized vortex interactions.