LAUSR

The interacting Bose–Hubbard flux ladder provides an ideal model to probe novel quantum phenomena of many-body systems. Here, we report on the first direct observation of dynamical quantum phase transition (DQPT) in interacting Bose–Hubbard flux ladder induced by defect perturbation, which provides a new scheme for experimental design and manipulation of the DQPT in ultracold atomic system. Under the mean-field approximation, DQPT is identified by resolving the order parameter and the temporal evolution of patterns of atomic density distributions and local current configurations of the system. The threshold for occurrence of DQPT is obtained analytical and the physical mechanism of DQPT is revealed explicitly. Periodic appearance and annihilation of dynamical vortex and the manifestation of symmetry restoration after perturbation from broken-symmetry phase are observed. A thorough connection among the order parameter dynamics, the underlying ground state phase transition and nonequilibrium dynamics is established in real time and real space for the first time. Interestingly, by quenching the defect, the underlying ground state phases are captured, which provides a feasible dynamical measurement scheme for the observation of the underlying ground state phase which is challenging to reach experimentally.