Quantum Gas Lab  @ Seoul National University

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We are an experimental research group in the Department of Physics and Astronomy, Seoul National University. Our group studies ultracold gases to investigate collective quantum phenomena such as Bose-Einstein condensation and superfluidity. Quantum gases are highly controllable and clean systems, presenting a new experimental avenue for fundamental study of quantum many-body physics. Our goal is to exploit and develop various quantum gas systems to search for new states of matter and to address challenging problems in condensed matter physics.

 

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Position Openings

If you are interested in joining us, please send your inquiry to yishin(at)snu.ac.kr .

 

 

 

Recent Research Highlights

 

 

Observation of von Kármán Vortex Street in an Atomic Superfluid Gas

Physical Review Letters 117, 245301 (2016)

We report on the experimental observation of vortex cluster shedding from a moving obstacle in an oblate atomic Bose-Einstein condensate. At low obstacle velocities v above a critical value, vortex clusters consisting of two like-sign vortices are generated to form a regular configuration like a von Kármán street, and as v is increased, the shedding pattern becomes irregular with many different kinds of vortex clusters. In particular, we observe that the Stouhal number associated with the shedding frequency exhibits saturation behavior with increasing v. The regular-to-turbulent transition of the vortex cluster shedding reveals remarkable similarities between a superfluid and a classical viscous fluid. Our work opens a new direction for experimental investigations of the superfluid Reynolds number characterizing universal superfluid hydrodynamics.

Related articles in Viewpoint in Physics and Physics Today

 

 

 

Half-Quantum Vortices in an Antiferromagnetic Spinor Bose-Einstein Condensate

Physical Review Letters 115, 015301 (2015)

We report on the observation of half-quantum vortices (HQVs) in the easy-plane polar phase of an antiferromagnetic spinor Bose-Einstein condensate. Using in situ agnetization-sensitive imaging, we observe that pairs of HQVs with opposite core magnetization are generated when singly charged quantum vortices are injected into the condensate. The dynamics of HQV pair formation is characterized by measuring the temporal evolutions of the pair separation distance and the core magnetization, which reveals the short-range nature of the repulsive interactions between the HQVs. We find that spin fluctuations arising from thermal population of transverse magnon excitations do not significantly affect the HQV pair formation dynamics. Our results demonstrate the instability of a singly charged vortex in the antiferromagnetic spinor condensate.

 

 

 

 

 

QGL@SNU,  Seoul 151-747, Korea. Tel +82(2)880-4233