Time: 10:00-11:30, Friday, March 25th, 2022
Venue: 4#311
Host: Prof. Congjun Wu
Speaker: Prof. Jinwu Ye, Mississippi State university
Title: Observing Quantum Phase transitions in a moving frame
Biography:
Prof. Ye received his Ph.D. from Yale University. Now he is a Professor at Mississippi state university. He has been a long-term visitor at the Institute for Theoretical Sciences, Westlake University since last Fall. Prof. Ye's research covers wide areas of theoretical physics such as condensed matter theory quantum optics, cold atom physics and quantum field theory. He mainly focuses on the emergent quantum and topological phenomena of interacting electrons, spins and photons, also extends to supersymmetry breaking, conformal field theory and quantum black holes from materials point of views.
Abstract:
The important role of Lorentz transformation (LT) and invariance (LI) in relativistic quantum field theory is well appreciated and understood. At a low velocity, the LT just reduces to the Galileo transformation (GT). While many body systems in materials or cold atom systems in a periodic lattice potential break the LI explicitly, therefor are non-relativistic. Unfortunately, the possible effects of GT in these non-relativistic quantum many-body systems were poorly understood. In this work, we explore its dramatic effects, especially near quantum phase transitions (QPT) which are among the most fantastic phenomena in Nature. We show that an observer in a different inertial frame may detect new quantum phases through novel quantum phase transitions. We demonstrate this new effect by studying one of the simplest QPTs: Superfluid (SF)-Mott transitions of interacting bosons in a square lattice observed in a frame moving with a constant velocity $ c $. We develop effective actions in the moving frame, then explore them by applying various methods such as mean field analysis, field theory renormalization group, charge-vortex duality and scaling analysis. The intrinsic interplay between the Galileo transformation and symmetry breaking in many body quantum systems are analyzed. The classical $ \hbar \to 0 $ limit is also examined. Contrast to the Doppler shifts in a relativistic quantum field theory and Unruh effects in an accelerating observer are made. The experimental detections in the moving frame are also discussed.
