Signatures of fragmentation for periodically driven fermions

The occurrence of prethermal Hilbert space fragmentation (HSF) in periodically driven quantum systems has its roots in the emergence of additional, approximate, kinetic constraints at special driving frequencies. Here, the authors show that the out-of-time-ordered correlators (OTOCs) of a driven fermion chain with open boundary condition exhibit a signature of such HSF. At the special drive frequencies where such prethermal HSF occurs, the OTOCs display periodic unscrambling of information, which provides a yet unexplored, experimentally testable, marker for prethermal fragmentation.