Mid-Term Report Summary - MICROQUANT (Microscopy of Tunable Many-Body Quantum Systems)
Samples of ultracold atoms and molecules confined to crystals of light are ideal quantum many-body model systems. They allow the study of novel phase transitions, unconventional forms of superconductivity and superfluidity, novel forms of magnetism, and, possibly, novel types of topological order. In particular, dynamical processes in a quantum many-body system can be studied with superb control. One hope is to build so-called quantum simulators that will outperform classical (computer) simulations of quantum many-body systems. This project is aimed at studying quantum many-body systems at the level of their microscopic constituents. For this, a new generation quantum-gas microscope apparatus is set up that will investigate the properties of Bose-Fermi quantum gas mixtures and fermionic dipolar quantum gases. In parallel, experiments are performed on an existing precursor apparatus. A recent highlight was the observation of many-body dynamics in long-range tunneling after a quantum quench (F. Meinert et al. Science 344, 1260 (2014)). 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 were able to 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 could be identified. Such higher order tunneling resonances have never been seen in nature before, and it is an interesting question whether electrons or Cooper pairs can undergo such processes in a similar way.