Ultrafast dynamics of cold Fermi gas after a local quench

We consider nonequilibrium dynamics of two initially independent reservoirs A and B filled with a cold Fermi gas coupled and decoupled by two quantum quenches following one another. We find that the von Neumann entropy production induced by the quench is faster than thermal transport between the reservoirs and defines the short-time dynamics of the system. We analyze the energy change in the system which adds up the heat transferred between A and B and the work done by the quench to uncouple the reservoirs. In the case when A and B interact for a short time, we notice an energy increase in both reservoirs upon decoupling. This energy gain results from the quench's work and does not depend on the initial temperature imbalance between the reservoirs. We relate the quench's work to the mutual correlations of A and B expressed through their von Neumann entropies. Utilizing this relation, we show that once A and B become coupled, their entropies grow (on a timescale of the Fermi time) faster than the heat flow within the system. This result may provide a track of quantum correlations' generation at finite temperatures which one may probe in ultracold atoms, where we expect the characteristic timescale of correlations' growth to be -0.1 ms.

Automated summary

We study the nonequilibrium dynamics of cold Fermi gas in two initially independent reservoirs A and B, which are coupled and decoupled by two consecutive quantum quenches. We find that the von Neumann entropy production induced by the quench is faster than thermal transport between the reservoirs and determines the short-time dynamics of the system. The energy change in the system, including the heat transfer between A and B and the work done by the quench, is analyzed. When A and B interact for a short time, an energy increase is observed in both reservoirs upon decoupling, and this energy gain is independent of the initial temperature difference between the reservoirs. We attribute the quench's work to the mutual correlations of A and B expressed through their von Neumann entropies. By considering this relation, we demonstrate that once A and B become coupled, their entropies grow faster (on the timescale of the Fermi time) than the heat flow within the system. This result offers insights into the generation of quantum correlations at finite temperatures, which can be probed in ultracold atoms with a characteristic timescale of correlation growth of -0.1 ms.