5,708 research outputs found
Many-Body Localization in the Infinite-Interaction Limit
We study the full many-body localization (MBL) in the Rydberg atomic quantum
simulator with quasiperiodic modulation. Employing both exact diagonalization
(ED) and time-evolving block decimation (TEBD) methods, we identify evidence of
a constrained many-body-localized phase stabilized by a pure quasirandom field
transverse to the direction of the projection. Intriguingly, through the lens
of quantum dynamics, we find that rotating the modulated field from parallel
towards perpendicular to the projection axis induces an eigenstate transition
between the diagonal and the constrained MBL phases. Remarkably, the growth of
the entanglement entropy in constrained MBL follows a double-logarithmic form,
whereas it changes to a power law in the diagonal limit. Although the diagonal
MBL steered by a strong modulation along the projection direction can be
understood by extending the phenomenology of local integrals of motion, a
thorough analysis of the constrained MBL calls for the new ingredients. As a
preliminary first step, we unveil the significance of confined nonlocal effects
in the integrals of motion of the constrained MBL phase, which potentially
challenges the established framework of the unconstrained MBL. Since the
quasiperiodic modulation has been achievable in cold-atom laboratories, the
constrained and diagonal MBL regimes, as well as the eigenstate transition
between them, should be within reach of the ongoing Rydberg experiments.Comment: 9 pages, 5 figure
Lieb-Robinson Bounds, Out-of-Time-Order Commutators, and Lightcone Structures of Unconventional Many-Body Localization in Constrained Quantum Systems
Study how quantum information propagates through the spacetime manifold may
provide a useful means of identifying, distinguishing, and classifying the
unconventional phases of matter fertilized by many-body effects in strongly
interacting systems in and out of equilibrium. Via a fuller characterization of
the key aspects regarding the descendent novel dynamical processes, we
performed such an analysis on the constrained many-body-localized phase -- a
newly-discovered fully localized state in the infinite-interaction limit -- in
the quasirandom Rydberg-blockaded spin chains using the thermal
out-of-time-ordered commutators (OTOCs). The calculated OTOC lightcone contours
predict a new and hitherto unknown Lieb-Robinson bound for the constrained
many-body localization, which is qualitatively different from that of the
conventional unconstrained many-body Anderson insulators normally arising in
the weak-interaction limit. Our combined numerical and analytical investigation
thus suggests that the constrained many-body localization is a distinct
dynamical phase of matter in constrained quantum systems whose underlying
mechanism of nonergodicity is beyond the existing phenomenology of quasilocal
integrals of motion. Further, it also consolidates the hierarchy of
unconventional quantum dynamics that encompasses constrained, unconstrained,
and diagonal many-body-localized states.Comment: 6 pages, 5 figures (main) and 18 pages (supp
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