ECE Seminar

Abstract:

Conventional phase transitions are abrupt changes in the equilibrium properties of a system as some knob (e.g., temperature or magnetic field) is tuned. In this talk, we will discuss purely dynamical phase transitions, across which the equilibrium state evolves smoothly but dynamical properties—ranging from the optical conductivity to the system’s ability to preserve quantum information in a retrievable form—abruptly change. Dynamical phase transitions can happen even in settings where equilibrium transitions are forbidden, such as at high temperature in one-dimensional systems; they occur alike in clean and disordered systems, isolated and open systems. 

I will survey what is known about the mechanisms driving these transitions, the experimental evidence for them, and the properties of the distinct dynamical phases they separate. I will close by presenting some recent experimental and numerical puzzles that have emerged from the study of such transitions, including the unexpectedly long persistence times of certain highly excited states, and the strongly non-Gaussian fluctuations of such states.

Bio:

Sarang Gopalakrishnan has been an assistant professor of physics at Penn State since 2021; prior to that, he was an assistant professor of physics at the City University of New York (2016-2020). He received his Ph.D. from the University of Illinois at Urbana-Champaign in 2012, and has held postdoctoral positions at Harvard (2012-2015) and Caltech (2015-2016). His interests span a variety of topics in condensed matter physics, atomic and optical physics, and quantum information science.