"X-ray coherent diffractive imaging of quantum vortices in helium droplets" by Andrey Vilesov (USC)

Thursday, May 12, 2016 - 4:00pm to 5:00pm
Physics and Astronomy Colloquium

Thursdays, 4:00-5:00 pm

1-434 Physics and Astronomy (map)
Reception from 3:30-4:00 p.m.
(unless otherwise posted)


Guest Speaker: Andrey Vilesov (University of Southern California)

Talk Title:  “O X-ray coherent diffractive imaging of quantum vortices in helium droplets”


Helium nanodroplets have long been considered ideal model systems to explore quantum hydrodynamics in self-contained, isolated superfluids. However, the dynamic properties of individual droplets, such as vorticity, remained beyond the reach of experimentalists. Here, we investigate the rotation of single, superfluid 4He droplets (D=200-2000 nm) via single-shot femtosecond X-ray coherent diffractive imaging.1  As indicated by large centrifugal deformations, the droplets’ angular velocities span a range from vanishing to those close to the disintegration limit. The shapes of rotating viscous and superfluid droplets are compared. The formation of quantum vortex lattices inside the droplets is confirmed by observing characteristic Bragg patterns from Xe clusters trapped in the vortex cores. The vortex densities are up to five orders of magnitude larger than observed in bulk liquid He, accessing a previously unattainable regime of quantum rotation. The images of the vortex filaments in the droplets were obtained from the diffraction images via phase retrieval techniques.2 Excessive doping by Xe changes equilibrium arrangement of vortices in the droplet and leads to stabilization of widely spaced configurations. Evidence for non-stationary vortex dynamics comes from observations of asymmetric formations of vortices in some droplets. This collaborative work was performed at Linac Coherent Light Source, the free electron laser within SLAC National Accelerator Laboratory.

1. L. F. Gomez et. al., Science, 345: 906-9 (2014).

2. R. M. Tanyag et. al., Structural Dynamics 2, 051102, (2015)

For more information, contact Jay Hauser


We thank the following people for their contributions to the wine fund for the post-colloquium reception:
Prof. Dolores Bozovic, Prof. Mike Cornwall, Prof. Bob Cousins, Prof. Andrea Ghez, Prof. Karoly Holczer, Prof. Eric Hudson, Robert Huff, Prof. Alex Kusenko, Prof. Myank Mehta, Prof. John Miao, Prof. Roberto Peccei, Prof. Claudio Pellegrini, Prof. David Saltzberg, Prof. Jean Turner and Prof. Ben Zuckerman.


Event Attachments: 
1-434 PAB