Emergence of Unruh prethermalization for uniformly accelerating many-atom system

Abstract: A uniformly accelerated atom in an inertial vacuum generally thermalizes and reaches a Gibbs state. This phenomenon is commonly known as the Unruh effect. Here, we show that the situation is entirely different for the many-atoms problem. In the case of non-interacting accelerating atoms, we show that a regime exists where the entire system reaches a prethermal generalized Gibbs state before it thermalizes. The prethermal state is protected by emergent conserved quantities; hence, the system behaves like a nearly-integrable one, which shows a sharp distinction from the Unruh effect. We coin the term ``Unruh prethermalization" to characterize this phenomenon. The measure of entanglement is a good estimation of the lifetime of the prethermal state and is consistent with previous studies. Finally, we show that in such a regime, the dynamics show a Dicke superradiance-type radiation burst before reaching the prethermal state. In contrast, only a mono-exponential decay is observed for Unruh thermalization. In addition, to highlight the significance of our results, we compare them with existing experimental observations.