46 research outputs found
Engineering a flux-dependent mobility edge in disordered zigzag chains
There has been great interest in realizing quantum simulators of charged
particles in artificial gauge fields. Here, we perform the first quantum
simulation explorations of the combination of artificial gauge fields and
disorder. Using synthetic lattice techniques based on parametrically-coupled
atomic momentum states, we engineer zigzag chains with a tunable homogeneous
flux. The breaking of time-reversal symmetry by the applied flux leads to
analogs of spin-orbit coupling and spin-momentum locking, which we observe
directly through the chiral dynamics of atoms initialized to single lattice
sites. We additionally introduce precisely controlled disorder in the site
energy landscape, allowing us to explore the interplay of disorder and large
effective magnetic fields. The combination of correlated disorder and
controlled intra- and inter-row tunneling in this system naturally supports
energy-dependent localization, relating to a single-particle mobility edge. We
measure the localization properties of the extremal eigenstates of this system,
the ground state and the most-excited state, and demonstrate clear evidence for
a flux-dependent mobility edge. These measurements constitute the first direct
evidence for energy-dependent localization in a lower-dimensional system, as
well as the first explorations of the combined influence of artificial gauge
fields and engineered disorder. Moreover, we provide direct evidence for
interaction shifts of the localization transitions for both low- and
high-energy eigenstates in correlated disorder, relating to the presence of a
many-body mobility edge. The unique combination of strong interactions,
controlled disorder, and tunable artificial gauge fields present in this
synthetic lattice system should enable myriad explorations into intriguing
correlated transport phenomena.Comment: 10 pages, 5 figures, 5 pages of supplementary materials; updated
version has additional dat
Superfluidity of Interacting Bosonic Mixtures in Optical Lattices
We report the observation of many-body interaction effects for a homonuclear
bosonic mixture in a three-dimensional optical lattice with variable state
dependence along one axis. Near the superfluid-to-Mott insulator transition for
one component, we find that the presence of a second component can reduce the
apparent superfluid coherence, most significantly when it either experiences a
strongly localizing lattice potential or none at all. We examine this effect by
varying the relative populations and lattice depths, and discuss the observed
behavior in view of recent proposals for scattering from impurities and of
atom-phonon coupling for atoms immersed in a superfluid.Comment: 4 pages, 3 figure
Synthetic dimensions in ultracold molecules: quantum strings and membranes
Synthetic dimensions alter one of the most fundamental properties in nature,
the dimension of space. They allow, for example, a real three-dimensional
system to act as effectively four-dimensional. Driven by such possibilities,
synthetic dimensions have been engineered in ongoing experiments with ultracold
matter. We show that rotational states of ultracold molecules can be used as
synthetic dimensions extending to many - potentially hundreds of - synthetic
lattice sites. Microwaves coupling rotational states drive fully controllable
synthetic inter-site tunnelings, enabling, for example, topological band
structures. Interactions leads to even richer behavior: when molecules are
frozen in a real space lattice with uniform synthetic tunnelings, dipole
interactions cause the molecules to aggregate to a narrow strip in the
synthetic direction beyond a critical interaction strength, resulting in a
quantum string or a membrane, with an emergent condensate that lives on this
string or membrane. All these phases can be detected using measurements of
rotational state populations.Comment: 5-page article + 4 figures + references; 7 pages + 4 figures in
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