By tuning the optical lattice
depth or the interaction between cold atoms, a weakly-interacting atomic
bosonic superfluid can be converted into a strongly correlated Mott insulator.
Near the phase boundary, quantum criticality, resembling that of Ising-type
magnetic systems in higher dimensions, is expected to emerge with full
universal behavior. Cold atom researchers in IRG4 have established the first in
situ imaging for bosonic atoms in 2D optical lattices, which provides a
powerful tool to capture the full quantum state of the many-body system, from
the microscopic statistics of site occupancy to the macroscopic thermodynamics. This experimental milestone has also been achieved along with very
interesting findings: observation of the long- sought plateau structure of the
Mott insulator, and the incompressibility of the Mott insulator domains.
New experiments to explore the quantum dynamics of atoms in the quantum
critical regime have shown interesting transport behavior in mass and entropy
flows. In particular, time scales very different from microsopic tunneling and
interaction time scales have been identified in the global equilibration of the
2D system.
