Optical manipulation of magnetically trapped superconducting micro particles in superfluid helium (Conference Presentation)

Laser ablation in superfluid helium, having extremely low temperature, negligibly small viscosity, huge thermal conductivity, and high transparency in visible region, provides us a unique opportunity to fabricate novel microstructures and control their motion. We have successfully fabricated nano and micro spheres of semiconductors by the laser ablation in the superfluid helium with a nanosecond Nd:YAG laser. [Scientific Reports 4, 5186 (2014).] Recently, we applied this method to metals, such as indium and rhenium, which show superconductivity at low temperature. To select superconducting particles, we utilized perfect diamagnetism caused by Meissner effect, designing a magnetic trap with two permanent magnets for the superconducting particles. Thus we fabricated and trapped a single or several superconducting particles after the laser ablation in the superfluid helium [Applied Physics Express 10, 022701(2017).] Here we successfully control the positions of the magnetically trapped superconducting particles, by irradiating a laser to them. The particles were pushed away from their original trapped positions and after the irradiation released from the displaced positions, moving along the force of the trapping potential and the viscosity force of the superfluid helium. By tracking the particles motion we can deduce physical properties of the superfluid helium and trapped particles. Thus the optical fabrication and manipulation of the superconducting micro particles provide us a unique opportunity to investigate superfluidity and superconductivity.