10 research outputs found
Observation of many-body localization in a one-dimensional system with single-particle mobility edge
We experimentally study many-body localization (MBL) with ultracold atoms in
a weak one-dimensional quasiperiodic potential, which in the noninteracting
limit exhibits an intermediate phase that is characterized by a mobility edge.
We measure the time evolution of an initial charge density wave after a quench
and analyze the corresponding relaxation exponents. We find clear signatures of
MBL, when the corresponding noninteracting model is deep in the localized
phase. We also critically compare and contrast our results with those from a
tight-binding Aubry-Andr\'{e} model, which does not exhibit a single-particle
intermediate phase, in order to identify signatures of a potential many-body
intermediate phase
Exploring the Single-Particle Mobility Edge in a One-Dimensional Quasiperiodic Optical Lattice
A single-particle mobility edge (SPME) marks a critical energy separating
extended from localized states in a quantum system. In one-dimensional systems
with uncorrelated disorder, a SPME cannot exist, since all single-particle
states localize for arbitrarily weak disorder strengths. However, if
correlations are present in the disorder potential, the localization transition
can occur at a finite disorder strength and SPMEs become possible. In this
work, we find experimental evidence for the existence of such a SPME in a
one-dimensional quasi-periodic optical lattice. Specifically, we find a regime
where extended and localized single-particle states coexist, in good agreement
with theoretical simulations, which predict a SPME in this regime
Observation of many-body localization of interacting fermions in a quasi-random optical lattice
We experimentally observe many-body localization of interacting fermions in a
one-dimensional quasi-random optical lattice. We identify the many-body
localization transition through the relaxation dynamics of an
initially-prepared charge density wave. For sufficiently weak disorder the time
evolution appears ergodic and thermalizing, erasing all remnants of the initial
order. In contrast, above a critical disorder strength a significant portion of
the initial ordering persists, thereby serving as an effective order parameter
for localization. The stationary density wave order and the critical disorder
value show a distinctive dependence on the interaction strength, in agreement
with numerical simulations. We connect this dependence to the ubiquitous
logarithmic growth of entanglement entropy characterizing the generic many-body
localized phase.Comment: 6 pages, 6 figures + supplementary informatio
Observation of Slow Dynamics near the Many-Body Localization Transition in One-Dimensional Quasiperiodic Systems.
In the presence of sufficiently strong disorder or quasiperiodic fields, an interacting many-body system can fail to thermalize and become many-body localized. The associated transition is of particular interest, since it occurs not only in the ground state but over an extended range of energy densities. So far, theoretical studies of the transition have focused mainly on the case of true-random disorder. In this work, we experimentally and numerically investigate the regime close to the many-body localization transition in quasiperiodic systems. We find slow relaxation of the density imbalance close to the transition, strikingly similar to the behavior near the transition in true-random systems. This dynamics is found to continuously slow down upon approaching the transition and allows for an estimate of the transition point. We discuss possible microscopic origins of these slow dynamics
Periodically driving a many-body localized quantum system
We experimentally study a periodically driven many-body localized system
realized by interacting fermions in a one-dimensional quasi-disordered optical
lattice. By preparing the system in a far-from-equilibrium state and monitoring
the remains of an imprinted density pattern, we identify a localized phase at
high drive frequencies and an ergodic phase at low ones. These two distinct
phases are separated by a dynamical phase transition which depends on both the
drive frequency and the drive strength. Our observations are quantitatively
supported by numerical simulations and are directly connected to the change in
the statistical properties of the effective Floquet Hamiltonian.We acknowledge support from Technical University of Munich - Institute for Advanced Study, funded by the German Excellence Initiative and the European Union FP7 under grant agreement 291763, from the DFG grant no. KN 1254/1-1, the European Commission (UQUAM, AQuS) and the Nanosystems Initiative Munich (NIM)
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Observation of Slow Dynamics near the Many-Body Localization Transition in One-Dimensional Quasiperiodic Systems.
In the presence of sufficiently strong disorder or quasi-periodic fields, an interacting many-body system can fail to thermalize and become many-body localized. The associated transition is of particular interest, since it occurs not only in the ground state but over an extended range of
energy densities. So far, theoretical studies of the transition have focused mainly on the case of true-random disorder. In this work, we experimentally and numerically investigate the regime close to the many-body localization transition in quasi-periodic systems. We find slow relaxation of the density imbalance close to the transition, strikingly similar to the behavior near the transition in true-random systems. This dynamics is found to continuously slow down upon approaching the
transition and allows for an estimate of the transition point. We discuss possible microscopic origins of these slow dynamics
Coupling Identical one-dimensional Many-Body Localized Systems.
We experimentally study the effects of coupling one-dimensional many-body localized systems with identical disorder. Using a gas of ultracold fermions in an optical lattice, we artificially prepare an initial charge density wave in an array of 1D tubes with quasirandom on-site disorder and monitor the subsequent dynamics over several thousand tunneling times. We find a strikingly different behavior between many-body localization and Anderson localization. While the noninteracting Anderson case remains localized, in the interacting case any coupling between the tubes leads to a delocalization of the entire system.We acknowledge financial support by the European Commision (UQUAM, AQuS) and the Nanosystems Initiative Munich (NIM).This is the author accepted manuscript. The final version is available from the American Physical Society via http://dx.doi.org/10.1103/PhysRevLett.116.14040
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QUANTUM GASES. Observation of many-body localization of interacting fermions in a quasirandom optical lattice.
Many-body localization (MBL), the disorder-induced localization of interacting particles, signals a breakdown of conventional thermodynamics because MBL systems do not thermalize and show nonergodic time evolution. We experimentally observed this nonergodic evolution for interacting fermions in a one-dimensional quasirandom optical lattice and identified the MBL transition through the relaxation dynamics of an initially prepared charge density wave. For sufficiently weak disorder, the time evolution appears ergodic and thermalizing, erasing all initial ordering, whereas above a critical disorder strength, a substantial portion of the initial ordering persists. The critical disorder value shows a distinctive dependence on the interaction strength, which is in agreement with numerical simulations. Our experiment paves the way to further detailed studies of MBL, such as in noncorrelated disorder or higher dimensions.We acknowledge financial support by the Deutsche Forschungsgemeinschaft (FOR801, Deutsch-Israelisches Kooperationsprojekt Quantum phases of ultracold atoms in optical lattices), the European Commission (UQUAM and AQuS), the U.S. Defense Advanced Research Projects Agency (Quantum Emulations of New Materials Using Ultracold Atoms), the Minerva Foundation, ISF grant no. 1594/11, Nanosystems Initiative Munich (NIM), and the Swiss Society of Friends of the Weizmann Institute