A quantum many-body bounce

Ultracold quantum gases offer a fascinating playground for exploring and understanding the fundamentals of out-of-equilibrium behaviour of quantum matter. Experimental systems whose many-body dynamics can be described by exactly solvable models play a particularly important role. A paradigmatic example in this realm is the Tonks-Girardeau (TG) gas of impenetrable bosons. Here we investigate and predict a striking dynamical manifestation of the impenetrability--a collective many-body bounce effect. This effect, while being invisible in the evolution of the in-situ density profile of the gas, can be revealed through a nontrivial narrowing of its momentum distribution during breathing-mode oscillations. To demonstrate this, we develop an exact finite-temperature dynamical theory of a harmonically trapped TG gas, thus extending on previous zero-temperature results and opening the way to solving arbitrary dynamical protocols of the TG gas. We identify physical regimes for observing the many-body bounce effect and foresee it as a valuable probe for characterising the nonequilibrium dynamics of interacting quantum fluids.