Abstract
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.
Highlights
The idea that the transport of quantum particles in a random environment can be completely arrested due to the interference of multiple transport pathways was first pointed out by Anderson six decades ago [1]
Cold-atom techniques in principle allow for the exploration of such physics in lower-dimensional systems, where mobility edges can be introduced by correlations in the applied disorder or modified lattice connectivities
This work represents the first direct observation of a single-particle mobility edge in lower dimensions, which is enabled by the unique ability to stably prepare atoms in any energy eigenstate and explore their localization properties in a system with precisely controlled disorder and tunable artificial gauge fields
Summary
The idea that the transport of quantum particles in a random environment can be completely arrested due to the interference of multiple transport pathways was first pointed out by Anderson six decades ago [1]. Despite the exquisite control over cold-atom systems and the observations of localization in one dimension over a decade ago, for both nearly random disorder [7] and correlated pseudodisorder [8], single-particle mobility edges (SPMEs) in lower dimensions have gone unexplored The reasons for this are somewhat technical—it is quite difficult to modify lattice connectivities, and the varieties of. Engineered disorder that have been explored in experiment have either been practically random (speckle disorder [5,6,7,9], with short-range correlations due to diffraction) or of a particular form of correlated disorder which, due to a peculiar fine-tuning, does not admit a SPME In the latter case, the pseudodisorder that arises in a lattice system due to shifts of the site energies by an added, weaker incommensurate lattice is well described by the Aubry-Andre (AA) model [8,10,11,12]. The influence of interactions is even more strongly evident in the case of the 1D AA with only NN tunneling, where a drastic shift in the localization transition is observed between low- and high-energy eigenstates, corresponding to a mobility edge driven purely by interparticle interactions
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