3,384 research outputs found
The chemical analysis experiment for the Surveyor lunar mission
Alpha particle detector experiment for chemical analysis of lunar surface by Surveyor spacecraf
Localization persisting under aperiodic driving
Localization may survive in periodically driven (Floquet) quantum systems, but is generally unstable for aperiodic drives. In this Letter, we identify a hidden conservation law originating from a chiral symmetry in a disordered spin-21 XX chain. This protects indefinitely long-lived localization for general-even aperiodic-drives. Therefore, rather counterintuitively, adding further potential disorder which spoils the conservation law delocalizes the system, via a controllable parametrically long-lived prethermal regime. This provides an example of persistent single-particle "localization without eigenstates.
Anomalous random multipolar driven insulators
It is by now well established that periodically driven quantum many-body systems can realize topological nonequilibrium phases without any equilibrium counterpart. Here we show that, even in the absence of time translation symmetry, nonequilibrium topological phases of matter can exist in aperiodically driven systems for tunably parametrically long prethermal lifetimes. As a prerequisite, we first demonstrate the existence of longlived prethermal Anderson localization in two dimensions under random multipolar driving. We then show that the localization may be topologically nontrivial with a quantized bulk orbital magnetization even though there are no well-defined Floquet operators. We further confirm the existence of this anomalous random multipolar driven insulator by detecting quantized charge pumping at the boundaries, which renders it experimentally observable
Quantum liquids of the S=3/2 Kitaev honeycomb and related Kugel-Khomskii models
The Kitaev honeycomb model (KHM) is unique among the spin- Kitaev
models due to a massive ground state quasi-degeneracy that hampered previous
numerical and analytical studies. In a recent work~\cite{jin2022unveiling}, we
showed how an SO(6) Majorana parton mean-field theory of the isotropic
KHM explains the anomalous features of this Kitaev spin liquid (KSL) in terms
of an emergent low-energy Majorana flat band. Away from the isotropic limit,
the KSL generally displays a quadrupolar order with gapped or gapless
Majorana excitations, features that were quantitatively confirmed by DMRG
simulations. In this paper, we explore the connection between the KHM
with Kugel-Khomskii models and discover new exactly soluble examples for the
latter. We perform a symmetry analysis for the variational parton mean-field
\emph{Ans{\"a}tze} in the spin and orbital basis for different quantum liquid
phases of the KHM. Finally, we investigate a proposed time-reversal
symmetry breaking spin liquid induced by a {[}111{]} single ion anisotropy and
elucidate its topological properties as well as experimental signatures, e.g.
an unquantized thermal Hall response.Comment: 17 pages, 9 figure
Fermionic response from fractionalization in an insulating two-dimensional magnet
Conventionally ordered magnets possess bosonic elementary excitations, called
magnons. By contrast, no magnetic insulators in more than one dimension are
known whose excitations are not bosons but fermions. Theoretically, some
quantum spin liquids (QSLs) -- new topological phases which can occur when
quantum fluctuations preclude an ordered state -- are known to exhibit Majorana
fermions as quasiparticles arising from fractionalization of spins. Alas,
despite much searching, their experimental observation remains elusive. Here,
we show that fermionic excitations are remarkably directly evident in
experimental Raman scattering data across a broad energy and temperature range
in the two-dimensional material -RuCl. This shows the importance of
magnetic materials as hosts of Majorana fermions. In turn, this first
systematic evaluation of the dynamics of a QSL at finite temperature emphasizes
the role of excited states for detecting such exotic properties associated with
otherwise hard-to-identify topological QSLs.Comment: 5 pages, 3 figure
Rigorous Bounds on the Heating Rate in Thue-Morse Quasiperiodically and Randomly Driven Quantum Many-Body Systems
The nonequilibrium quantum dynamics of closed many-body systems is a rich yet challenging field. While recent progress for periodically driven (Floquet) systems has yielded a number of rigorous results, our understanding on quantum many-body systems driven by rapidly varying but aperiodic and quasiperiodic driving is still limited. Here, we derive rigorous, nonperturbative, bounds on the heating rate in quantum many-body systems under Thue-Morse quasiperiodic driving and under random multipolar driving, the latter being a tunably randomized variant of the former. In the process, we derive a static effective Hamiltonian that describes the transient prethermal state, including the dynamics of local observables. Our bound for Thue-Morse quasiperiodic driving suggests that the heating time scales like (omega/g)(-C) (ln()(omega/)(g)) with a positive constant C and a typical energy scale g of the Hamiltonian, in agreement with our numerical simulations
An Exact Chiral Amorphous Spin Liquid
Topological insulator phases of non-interacting particles have been
generalized from periodic crystals to amorphous lattices, which raises the
question whether topologically ordered quantum many-body phases may similarly
exist in amorphous systems? Here we construct a soluble chiral amorphous
quantum spin liquid by extending the Kitaev honeycomb model to random lattices
with fixed coordination number three. The model retains its exact solubility
but the presence of plaquettes with an odd number of sides leads to a
spontaneous breaking of time reversal symmetry. We unearth a rich phase diagram
displaying Abelian as well as a non-Abelian quantum spin liquid phases with a
remarkably simple ground state flux pattern. Furthermore, we show that the
system undergoes a finite-temperature phase transition to a conducting thermal
metal state and discuss possible experimental realisations.Comment: 5 pages, 3 figure
Adaptation and enslavement in endosymbiont-host associations
The evolutionary persistence of symbiotic associations is a puzzle.
Adaptation should eliminate cooperative traits if it is possible to enjoy the
advantages of cooperation without reciprocating - a facet of cooperation known
in game theory as the Prisoner's Dilemma. Despite this barrier, symbioses are
widespread, and may have been necessary for the evolution of complex life. The
discovery of strategies such as tit-for-tat has been presented as a general
solution to the problem of cooperation. However, this only holds for
within-species cooperation, where a single strategy will come to dominate the
population. In a symbiotic association each species may have a different
strategy, and the theoretical analysis of the single species problem is no
guide to the outcome. We present basic analysis of two-species cooperation and
show that a species with a fast adaptation rate is enslaved by a slowly
evolving one. Paradoxically, the rapidly evolving species becomes highly
cooperative, whereas the slowly evolving one gives little in return. This helps
understand the occurrence of endosymbioses where the host benefits, but the
symbionts appear to gain little from the association.Comment: v2: Correction made to equations 5 & 6 v3: Revised version accepted
in Phys. Rev. E; New figure adde
Quantum many-body scars in optical lattices
The concept of quantum many-body scars has recently been put forward as a route to describe weak ergodicity breaking and violation of the eigenstate thermalization hypothesis. We propose a simple setup to generate quantum many-body scars in a doubly modulated Bose-Hubbard system which can be readily implemented in cold atomic gases. The dynamics are shown to be governed by kinetic constraints which appear via density-assisted tunneling in a high-frequency expansion. We find the optimal driving parameters for the kinetically constrained hopping which leads to small isolated subspaces of scared eigenstates. The experimental signatures and the transition to fully thermalizing behavior as a function of driving frequency are analyzed
An Instrument for Lunar Surface Chemical Analysis
Instrument for lunar surface chemical analysis that uses interactions with matter of monoenergetic alpha particle
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