Novel phases of matter with artificial quantum simulators: disorder and correlations in equilibrium and out-of-equilibrium many-body quantum lattices
The experiment, in the contest of the project ArtiQuS supported by MIUR (RBFR12NLNA), has the overall goal to investigate different quantum phases of lattice bosons in the presence of disorder and in out-of-equilibrium systems. The experiment is developed on an ultra cold atoms set-up hosted at European Laboratory for Non-Linear Spectroscopy (LENS), where we are able to produce 1D bosonic systems withcontrollable disorder and interaction, and in collaboration with the theoretical units located at Scuola Normale Superiore (SNS) in Pisa and at University of Padova. On the first topic we plan to fully characterise the strongly correlated regime in the presence of disorder at finite temperature. By establishing a connection with the zero temperature theory, this will lead to the first true characterization of the various quantum phases expected for a disordered bosonic system. On the second topic, we will study the thermalization of a one-dimensional many-body system in the presence of a quantum quench crossing a quantum phase transition. The combination of the out-of-equilibrium dynamics with disorder will open a new fascinating field of study.
ArtiQuS started in March 2013 and at state of the art focused on the characterization of the first topic. Combining measurements of coherence, transport and excitation spectra, we get evidence of an insulating regime extending from weak to strong interaction and surrounding a superfluidlike regime, in general agreement with the theory performed at zero temperature . This first comparison of finite temperature experiment with the zero-temperature theory open the path to a pioneering investigation of the effect of temperature on a disordered bosonic insulator .
We have also studied the momentum-dependent transport of 1D disordered bosons and employing the vanishing of the critical momentum for the observed instability we locate the fluid-insulator transition driven by disorder, across the interaction-disorder plane . The observed instability suggests a quantum activation of phase slip, but a detailed study of the damping rates measured on the oscillation in a weak lattice has been necessary to determine the quantum nature of phase slips events .
The present studies open the path to explore the role of temperature, also in connection with models for the many-body localization .
 C. D’Errico, E. Lucioni, L. Tanzi, L. Gori, G. Roux, I. P. McCulloch, T. Giamarchi, M. Inguscio, and G. Modugno, Observation of a Disordered Bosonic Insulator from Weak to Strong Interactions, Phys. Rev. Lett. 113, 095301 (2014).
 L. Gori et al., Finite temperature effects on a disordered bosonic insulator, to be submitted.
L. Tanzi, E. Lucioni, S. Chaudhuri, L. Gori, A. Kumar, C. D’Errico, M. Inguscio, and G. Modugno, Transport of a Bose Gas in 1D Disordered Lattices at the Fluid-Insulator Transition, Phys. Rev. Lett.111, 115301 (2013).
 L. Tanzi et al., Evidence of quantum phase slips in 1D atomic superfluids, to be submitted.
 I.L. Aleiner, B.L. Altshuler, and G.V. Shlyapnikov, A finite-temperature phase transition for disordered weakly interacting bosons in one dimension, Nat. Phys. 6, 900 (2010).