Professor Hua Bi zeng and doctoral student Chuan Yin Xia,  in cooperation with Professor Adolfo del Campo from University of Luxembourg published a paper titled “Universal Breakdown of Kibble-Zurek Scaling in Fast Quenches across a Phase Transition” in the new issue of Physical Review Letters.

The paper is available at: https://doi.org/10.1103/PhysRevLett.130.060402

Understanding the universality behind phase transitions is one of the most interesting topics in physics.  For equilibrium second order (continuous) phase transitions,  the universal scaling laws across the critical point have been understood well by the Ginzburg-Landau-Wilson paradigm. While for non-equilibrium phase transitions, due to the highly nonlinear dynamics cross the critical point and the anisotropy, it is always not an easy task to reveal the possible universality of the dynamics, if it exists.  The Kibble–Zurek mechanism (KZM) describes the non-equilibrium dynamics and found the universality of  topological defects formation in a system which is driven through a continuous phase transition at a finite rate. It is named after Tom W. B. Kibble, who pioneered the study of domain structure formation in the early universe, and Wojciech H. Zurek, who related the number of the defects to the critical exponents of the transition and to the rate of how fast the critical point is traversed.

Such a universality has been examined by many researchers in the laboratory. What is surprising is that, in recent experiments of fast quenches across the critical point, the defect density turned out to be a constant independent of quench rate. This phenomenon is beyond the KZM framework. In the current work, Prof. Zeng and co-authors focused on the experimentally observed deviations from KZM in rapid quenches and established their universality. While KZM scaling holds below a critical quench rate, for faster quenches the defect density and the freeze-out time become independent of the quench rate and exhibit a universal power-law scaling with the final value of the control parameter. These predictions are verified in several paradigmatic scenarios in both the classical and quantum domains.