Prethermal Fragmentation in a Periodically Driven Fermionic Chain

We study a fermionic chain with nearest-neighbor hopping and density-density interactions, where the nearest-neighbor interaction term is driven periodically. We show that such a driven chain exhibits prethermal strong Hilbert space fragmentation (HSF) in the high drive amplitude regime at specific drive frequencies ωₘ*. This constitutes the first realization of HSF for out-of-equilibrium systems. We obtain analytic expressions of ωₘ* using a Floquet perturbation theory and provide exact numerical computation of entanglement entropy, equal-time correlation functions, and the density autocorrelation of fermions for finite chains. All of these quantities indicate clear signatures of strong HSF. We study the fate of the HSF as one tunes away from ωₘ* and discuss the extent of the prethermal regime as a function of the drive amplitude.