2014•ScienceOpen access
Shapes and vorticities of superfluid helium nanodroplets
Luis F. Gomez, Ken Ferguson, James Cryan, Camila Bacellar, Rico Mayro P. Tanyag, Curtis F. Jones, Sebastian Schorb, Denis Anielski, Ali Belkacem, Charles Bernando, Rebecca Boll, John D. Bozek, Sebastian Carron, Gang Chen, Tjark Delmas, Lars Englert, Sascha W. Epp, Benjamin Erk, L. Foucar, Robert Hartmann, Alexander Hexemer, Martin Huth, Justin J. Kwok, Stephen R. Leone, H. Jonathan, Filipe R. N. C. Maia, Erik Malmerberg, Stefano Marchesini, Daniel M. Neumark, Billy K. Poon, James S. Prell, Daniel Rolles, Benedikt Rudek, Artem Rudenko, Martin Seifrid, Katrin R. Siefermann, Felix Sturm, Michele Swiggers, J. Ullrich, Fabian Weise, Petrus H. Zwart, Christoph Bostedt, Oliver Geßner, Andrey F. Vilesov
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Abstract
Helium nanodroplets are considered ideal model systems to explore quantum hydrodynamics in self-contained, isolated superfluids. However, exploring the dynamic properties of individual droplets is experimentally challenging. In this work, we used single-shot femtosecond x-ray coherent diffractive imaging to investigate the rotation of single, isolated superfluid helium-4 droplets containing ~10(8) to 10(11) atoms. The formation of quantum vortex lattices inside the droplets is confirmed by observing characteristic Bragg patterns from xenon clusters trapped in the vortex cores. The vortex densities are up to five orders of magnitude larger than those observed in bulk liquid helium. The droplets exhibit large centrifugal deformations but retain axially symmetric shapes at angular velocities well beyond the stability range of viscous classical droplets.
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