  Impurity injection into superfluid helium is a simple yet unique method with
diverse applications, including high-precision spectroscopy, quantum computing,
nano/micro materialsynthesis, and flow visualisation. Quantised vortices are
believed to play a major role in the interaction between superfluid helium and
light impurities. However, the basic principle governing the interaction is
still controversial for dense materials such as semiconductor and metal
impurities. Herein, we provide experimental evidence of the attraction of the
dense silicon nanoparticles to the quantised 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 quantised vortex cores. We also observed that two accidentally
intersecting quantised vortices exchanged their parts, a phenomenon called
quantised vortex reconnection. This behaviour closely matches the dynamical
scaling of reconnections. Our results provide a new method for visualising and
studying impurity-quantised vortex interactions.

Superconductivity;Optics