1,253 research outputs found
Relaxation and thermalization in the one-dimensional Bose-Hubbard model: A case study for the interaction quantum quench from the atomic limit
Motivated by recent experiments, we study the relaxation dynamics and
thermalization in the one-dimensional Bose-Hubbard model induced by a global
interaction quench. Specifically, we start from an initial state that has
exactly one boson per site and is the ground state of a system with infinitely
strong repulsive interactions at unit filling. Using exact diagonalization and
the density matrix renormalization group method, we compute the time dependence
of such observables as the multiple occupancy and the momentum distribution
function. Typically, the relaxation to stationary values occurs over just a few
tunneling times. The stationary values are identical to the so-called diagonal
ensemble on the system sizes accessible to our numerical methods and we further
observe that the micro-canonical ensemble describes the steady state of many
observables reasonably well for small and intermediate interaction strength.
The expectation values of observables in the canonical ensemble agree
quantitatively with the time averages obtained from the quench at small
interaction strengths, and qualitatively provide a good description of
steady-state values even in parameter regimes where the micro-canonical
ensemble is not applicable due to finite-size effects. We discuss our numerical
results in the framework of the eigenstate thermalization hypothesis. Moreover,
we also observe that the diagonal and the canonical ensemble are practically
identical for our initial conditions already on the level of their respective
energy distributions for small interaction strengths. Finally, we discuss
implications of our results for the interpretation of a recent sudden expansion
experiment [Phys. Rev. Lett. 110, 205301 (2013)], in which the same interaction
quench was realized.Comment: 19 pages, 22 figure
Back from the Future. Review of: Chukhrov, Kethi: Practising the Good: Desire and Boredom in Soviet Socialism. Minneapolis: eflux/University of Minnesota Press 2020
Quantum phases and topological properties of interacting fermions in one-dimensional superlattices
The realization of artificial gauge fields in ultracold atomic gases has
opened up a path towards experimental studies of topological insulators and, as
an ultimate goal, topological quantum matter in many-body systems. As an
alternative to the direct implementation of two-dimensional lattice
Hamiltonians that host the quantum Hall effect and its variants, topological
charge-pumping experiments provide an additional avenue towards studying
many-body systems. Here, we consider an interacting two-component gas of
fermions realizing a family of one-dimensional superlattice Hamiltonians with
onsite interactions and a unit cell of three sites, whose groundstates would be
visited in an appropriately defined charge pump. First, we investigate the
grandcanonical quantum phase diagram of individual Hamiltonians, focusing on
insulating phases. For a certain commensurate filling, there is a sequence of
phase transitions from a band insulator to other insulating phases (related to
the physics of ionic Hubbard models) for some members of the manifold of
Hamiltonians. Second, we compute the Chern numbers for the whole manifold in a
many-body formulation and show that, related to the aforementioned quantum
phase transitions, a topological transition results in a change of the value
and sign of the Chern number. We provide both an intuitive and conceptual
explanation and argue that these properties could be observed in quantum-gas
experiments
Latitudinal variation of the solar photospheric intensity
We have examined images from the Precision Solar Photometric Telescope (PSPT)
at the Mauna Loa Solar Observatory (MLSO) in search of latitudinal variation in
the solar photospheric intensity. Along with the expected brightening of the
solar activity belts, we have found a weak enhancement of the mean continuum
intensity at polar latitudes (continuum intensity enhancement
corresponding to a brightness temperature enhancement of ).
This appears to be thermal in origin and not due to a polar accumulation of
weak magnetic elements, with both the continuum and CaIIK intensity
distributions shifted towards higher values with little change in shape from
their mid-latitude distributions. Since the enhancement is of low spatial
frequency and of very small amplitude it is difficult to separate from
systematic instrumental and processing errors. We provide a thorough discussion
of these and conclude that the measurement captures real solar latitudinal
intensity variations.Comment: 24 pages, 8 figs, accepted in Ap
Interaction quantum quenches in the one-dimensional Fermi-Hubbard model with spin imbalance
Using the time-dependent density matrix renormalization group method and
exact diagonalization, we study the non-equilibrium dynamics of the
one-dimensional Fermi-Hubbard model following a quantum quench or a ramp of the
onsite interaction strength. For quenches from the non-interacting to the
attractive regime, we investigate the dynamical emergence of
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) correlations, which at finite spin
polarizations are the dominant two-body correlations in the ground state, and
their signatures in the pair quasi-momentum distribution function. We observe
that the post-quench double occupancy exhibits a maximum as the interaction
strength becomes of the order of the bandwidth. Finally, we study quenches and
ramps from attractive to repulsive interactions, which imprint FFLO
correlations onto repulsively bound pairs. We show that a quite short ramp time
is sufficient to wipe out the characteristic FFLO features in the post-quench
pair momentum distribution functions.Comment: 13 pages, 15 figures, minor revisions, version as publishe
Physical-mechanical properties and multilayer hierarchically organized structure of Ti-Ta-based surface alloy synthesized on the NiTi-substrate by high-current pulsed electron beam
Magnon Heat Transport in doped
We present results of the thermal conductivity of and single-crystals which represent model systems for the
two-dimensional spin-1/2 Heisenberg antiferromagnet on a square lattice. We
find large anisotropies of the thermal conductivity, which are explained in
terms of two-dimensional heat conduction by magnons within the CuO planes.
Non-magnetic Zn substituted for Cu gradually suppresses this magnon thermal
conductivity . A semiclassical analysis of
is shown to yield a magnon mean free path which scales
linearly with the reciprocal concentration of Zn-ions.Comment: 4 pages, 3 figure
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