The Sidney Nagel prize was established in 2019 to award an undergraduate or graduate student in a range of disciplines across the sciences whose original science includes beguiling imagery.  This award, in honor of physicist Sidney Nagel, was donated by his friends and colleagues.

2019 Prize winner: Lei Feng

Dr. Lei Feng was a graduate student at the University of Chicago (2013~2019) working in Cheng Chin's research group on experimental atomic physics. He graduated in 2019 with a Ph.D. in Physics and is current a postdoctoral scholar at the University of Maryland.

Citation: "For his innovative analysis and graphical presentation of Bose fireworks emission from atomic Bose-Einstein condensates."

What is Bose firework?    "Bose fireworks" refers to a sudden burst of thin atomic jets escaping from a driven Bose-Einstein condensate, which was discovered in 2017 by the Chin group. The emission occurs when the condensate is subject to modulation of atomic interactions. The jet structure results from inelasstic collisions between atoms, which is induced and amplified by the modulation. The following video show the beautiful "firworks" emission as the jets escape from the condensate:

Bose Fireworks emission with atomic interactions modulated at 2.5 KHz

What did Feng Lei find?      Dr. Lei Feng discovered that there is much more to the pattern than meets the eye. He employed novel algorithmns to analyze the emission and identified an unexpected "turtle" pattern in the correlation. His analysis and findings are reported in two publications:

1. High-harmonic Generation and the Hidden Turtle Pattern.

Lei and coworkers observed in 2018 that excited atoms experience multiple collisions and display an intriguing correlations resulting from the high-harmonic geration of matterwaves. The physics behind high-harmonic generation is illustrated below:

The first and high-harmonic generation of matter-wave jets 

Lei developed a pattern recognition algorithm to reveal the angular pattern in the seemingly random jet emission structure because the hidden pattern is randomly oriented with different strengths in each experiment. To align them, Lei rotated 209 images of jet structure acquired from independent experiments to maximize the angular variance of the averaged image. The  "Turtle" pattern  shows the complex correlation between different momentum modes:

Finding the hidden turtle  

Pattern recognition 

The turtle pattern obtained from the algorithm reflects all the possible correlations between emitted jets. We can think of that at whatever angle a "turtle head" appears, ther will be "tail" and "legs" that appear at the corresponding angles relative the "head". This angular cocurrance gives us clues which microscopic collisional processes produces such jet structure. This work is published in "Correlations in high harmonic generation of matter-wave jsts reveals by pattern recognition", Lei Feng, Jiazhong Hu, Logan Clark, Cheng Chin, Science 363, 521 (2019).

2. Phase correlation in jets

Lei and coworkers also found that the emitted atoms give a thermal-like Boltzmann distribution. This relates the jets emission to the intriguing Unruh radiation discussed in the context of graviational physics that an accelerating observer perceives the Minkowskii vacuum in an inertial frame as thermal source. To show that the emission is coherent in nature. Lei developed the scheme to interfere two waves of matterwave jets. The interference of the matterwave confirned the phase coherence of the "thermal emission". This works confirms the mind-boggling prediction that a thermal source to the local observers can in fact be a pure macroscopic quantum state. The work is published in "Quantum Simulation of Unruh Radiation", Jiazhong Hu, Lei Feng, Zhendong and Cheng Chin in Nature Physics 15, 785 (2019). 

Interfering two sets of jets excited by two consecutive pulses 

Interference of jets