Visualisation of quantised vortex reconnection as enabled by laser ablation

Abstract

Impurity injection into superfluid helium is a simple yet unique method with diverse applications, including high-precision spectroscopy[1-3], quantum computing[4], nano/micro material synthesis [5,6], and flow visualisation [7]. Quantised vortices are believed to play a major role in the interaction between superfluid helium and light impurities [2,[8][9][10][11]. However, the basic principle governing the interaction is still controversial for dense materials such as semiconductor and metal impurities [5,12]. Herein, we provide experimental evidence of the attraction of the dense silicon nanoparticles to the quantised vortex cores. We prepared the silicon nanoparticles via insitu 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 [13]. This behaviour closely matches the dynamical scaling of reconnections.Our results provide a new method for visualising and studying impurity-quantised vortex interactions.

Optical trapping of silicon nanoparticles in superfluid helium

“…Our result demonstrates the optical trapping of silicon nanoparticle in superfluid helium. The silicon nanoparticles are proven to be useful for the visualization of the quantized vortex structure in superfluid helium; silicon nanoparticles are trapped and stabilized along the quantized vortex cores [5]. Therefore, the current study would also provide us the opportunity for the optical manipulation of the quantized vortex structures meditated by the optically trapped silicon nanoparticles.…”