Speaker: Cheng Chin (James Franck institute, Enrico Fermi institute, and Department of Physics, University of Chicago)

Time: March 24, 2017 10:00

Place: 物理系C302报告厅

Abstract： Phase transitions are both ubiquitous and fascinating. Snow from the sky, a result of a phase transition, is run-of-the-mill in Chicago; however, we remain intrigued when realizing that the beautiful crystals of a snow flake, millimeter in size, grows from the molecular structure at the nano-meter scale. Beyond classical systems, an exponential growth of new symmetry across a phase transition, called inflation, reaches frontier of research on quantum many-body dynamics, as well as in the evolution of early universe. Based on a cesium Bose-Einstein condensate driven across a quantum phase transition, we have observed in the past years a series of interesting phenomena: emergence of topological defects (domain walls), exotic excitations (rotons), as well as the scaling symmetry of temporospatial correlations (Kibble-Zurek mechanism). A fundamental question I will address in this talk is: Is inflation a symmetry-breaking process that follows the second law of thermodynamics, or a quantum coherent process that is unitary and reversible? Bio: Cheng Chin has established the first research group devoted to studying ultracold atoms and molecules at the University of Chicago. Chin’s experiments are designed to achieve temperatures just billionths of a degree above absolute zero (minus 459.67 degrees Fahrenheit). Much of his research focuses on how ultracold molecules form a superfluid, a new state of matter that exists only at ultralow temperatures. Superfluids exhibit characteristics distinctively different from the solids, liquids and gases that dominate everyday life. Chin also uses ultracold technology to simulate the physics of the universe in the first moments following the big bang, and for the development of quantum computers. His honors include a Humboldt Research Fellowship and the American Physical Society's I.I. Rabi Prize.