@article{Nonequilibrium:1836,
      recid = {1836},
      author = {Feng, Lei},
      title = {Coherent Nonequilibrium Many-body Dynamics in Driven Bose  Condensates},
      publisher = {University of Chicago},
      school = {Ph.D.},
      address = {2019-06},
      pages = {188},
      abstract = {The understanding of quantum many-body physics is the key  to develop new quantum technologies including novel quantum  materials, high-precision sensors, and quantum computers.  However, understanding the general quantum many-body  physics is extremely difficult, particularly when such  systems are driven far from an equilibrium state. Ultracold  atoms, a clean, fully controllable, and coherent quantum  many-body systems can provide useful insights into the  fundamental properties of quantum matter. This thesis  discusses experiments on studying nonequilibrium dynamics  in driven ultracold bosonic atoms with fantastic static and  dynamical controls of the inter-particle interactions  through Feshbach resonances and external trapping  potentials using optical lattices and digital micromirror  device (DMD). 

With this versatile apparatus, we first  study the critical dynamics across a quantum phase  transition in shaken optical lattices.  Across a  ferromagnetic transition where the $\mathbb{Z}_2$ inversion  symmetry is broken, we are interested in how the system  evolves toward the new ground states generally with a  different symmetry. Utilizing the phase imprinting  technique with DMD,  we show that the macroscopic coherence  is maintained across the phase transition, the system  undergoes a coherent population transfer of particles  toward lower energy states and quantum fluctuations  determine the domain structure but do not destroy the  macroscopic coherence. 

We then present the complex  correlations rising from the matter-wave version of a  high-harmonic generation with oscillating interaction. This  high-harmonic generation of matterwave is a result of  stimulated secondary collisions. The stimulated primary  collisions, two condensate atoms collide absorbing one  energy quantum from the oscillating field, give rise to the  first observation of Bose fireworks. The scattered atoms  from the primary collisions can further collide with each  other or the ground-state atoms from the condensate and  such secondary collisions promote atoms to higher momentum  modes. Moreover, we show the density-wave dynamics prior to  the jets emission within the condensate with oscillating  interactions and explain the asymmetry in the jets emission  pattern based on near-field interference. Besides, we  further demonstrate the spatial and temporal phase  coherence of the emitted jets using matter-wave  interference and connect our matter-wave jets emission to  the famous Unruh radiation in relativistic physics.},
      url = {http://knowledge.uchicago.edu/record/1836},
      doi = {https://doi.org/10.6082/uchicago.1836},
}