We study non-equilibrium dynamics for an ensemble of tilted one-dimensional atomic Bose-Hubbard chains after a sudden quench to the vicinity of the transition point of the Ising paramagnetic to anti-ferromagnetic quantum phase transition. The quench results in coherent oscillations for the orientation of effective Ising spins, detected via oscillations in the number of doubly-occupied lattice sites. We characterize the quench by varying the system parameters. We report significant modification of the tunneling rate induced by interactions and show clear evidence for collective effects in the oscillatory response.PACS numbers: 37.10. Jk, 67.85.Hj, 75.10.Pq, 05.30.Rt Ultracold atomic ensembles confined in optical lattice potentials have proven to offer unique access to the study of strongly correlated quantum phases of matter [1, 2]. Unprecedented control over system parameters as well as exceptionally good isolation from the environment allow for implementation and quantitative simulation of lattice Hamiltonians [3, 4], not only bridging the fields of atomic and condensed matter physics in the study of ground-state phases, but also opening fundamentally new opportunities to explore out-of-equilibrium physics in essentially closed quantum systems [5, 6]. For example, the rapid time-dependent control available over system parameters makes it possible to observe dynamics arising from a quantum quench, where a parameter such as the lattice depth is changed suddenly in time [7][8][9]. Recently it was demonstrated that 1D chains of bosonic atoms with a superimposed linear gradient potential exhibit a quantum phase transition to a density-wave-ordered state, in which empty sites alternate with doubly-occupied sites ("doublons"). Beginning in a Mott-insulator phase of a BoseHubbard (BH) system [10, 11], where the on-site interactions dominate over tunneling and the atoms are exponentially localized on individual lattice sites, a gradient potential is added until the potential difference between adjacent sites matches the on-site interaction energy, and atoms can again resonantly tunnel. This was monitored for individual 1D chains with a length of about 10 sites with the quantum gas microscopy technique [12], and effectively maps onto a 1D Ising model [13], making it possible to simulate the transition from 1D paramagnetic (PM) spin chains to anti-ferromagnetic (AFM) spin chains in the context of ultracold atoms.In this letter, we explore the dynamics of a quantum quench for bosonic atoms in such a tilted optical lattice [14][15][16]. Specifically, we quench the strength of the tilt to be near the phase transition point between PM and AFM regimes, and hence take the system far out of equilibrium, inducing strong oscillations in the number of doublons, which we detect through molecule formation. We find clear indications for the collective character of the ensuing dynamics.We consider a 1D atomic ensemble in a tilted optical lattice potential near zero temperature. For sufficiently weak interaction energy, much smaller ...

Probing the Excitations of a Lieb-Liniger Gas from Weak to Strong CouplingMeinert, F.; Panfil, M.K.; Mark, M. J.; Lauber, K.; Caux, J.S.; Nägerl, H.-C. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Download date: 11 May 2018Probing the Excitations of a Lieb-Liniger Gas from Weak to Strong Coupling We probe the excitation spectrum of an ultracold one-dimensional Bose gas of cesium atoms with a repulsive contact interaction that we tune from the weakly to the strongly interacting regime via a magnetic Feshbach resonance. The dynamical structure factor, experimentally obtained using Bragg spectroscopy, is compared to integrability-based calculations valid at arbitrary interactions and finite temperatures. Our results unequivocally underlie the fact that holelike excitations, which have no counterpart in higher dimensions, actively shape the dynamical response of the gas.

We report on the experimental implementation of tunable occupation-dependent tunneling in a Bose-Hubbard system of ultracold atoms via time-periodic modulation of the on-site interaction energy. The tunneling rate is inferred from a time-resolved measurement of the lattice site occupation after a quantum quench. We demonstrate coherent control of the tunneling dynamics in the correlated many-body system, including full suppression of tunneling as predicted within the framework of Floquet theory. We find that the tunneling rate explicitly depends on the atom number difference in neighboring lattice sites. Our results may open up ways to realize artificial gauge fields that feature density dependence with ultracold atoms.

Quantum tunneling is at the heart of many low-temperature phenomena. In strongly correlated lattice systems, tunneling is responsible for inducing effective interactions, and long-range tunneling substantially alters many-body properties in and out of equilibrium. We observe resonantly enhanced long-range quantum tunneling in one-dimensional Mott-insulating Hubbard chains that are suddenly quenched into a tilted configuration. Higher-order tunneling processes over up to five lattice sites are observed as resonances in the number of doubly occupied sites when the tilt per site is tuned to integer fractions of the Mott gap. This forms a basis for a controlled study of many-body dynamics driven by higher-order tunneling and demonstrates that when some degrees of freedom are frozen out, phenomena that are driven by small-amplitude tunneling terms can still be observed.

We perform precision measurements on a Mott-insulator quantum state of ultracold atoms with tunable interactions. We probe the dependence of the superfluid-to-Mott-insulator transition on the interaction strength and explore the limits of the standard Bose-Hubbard model description. By tuning the on-site interaction energies to values comparable to the interband separation, we are able to quantitatively measure number-dependent shifts in the excitation spectrum caused by effective multibody interactions.