626 research outputs found
Condensate fragmentation as a sensitive measure of the quantum many-body behavior of bosons with long-range interactions
The occupation of more than one single-particle state and hence the emergence
of fragmentation is a many-body phenomenon universal to systems of spatially
confined interacting bosons. In the present study, we investigate the effect of
the range of the interparticle interactions on the fragmentation degree of one-
and two-dimensional systems. We solve the full many-body Schr\"odinger equation
of the system using the recursive implementation of the multiconfigurational
time-dependent Hartree for bosons method, R-MCTDHB. The dependence of the
degree of fragmentation on dimensionality, particle number, areal or line
density and interaction strength is assessed. It is found that for contact
interactions, the fragmentation is essentially density independent in two
dimensions. However, fragmentation increasingly depends on density the more
long-ranged the interactions become. The degree of fragmentation is increasing,
keeping the particle number fixed, when the density is decreasing as
expected in one spatial dimension. We demonstrate that this remains,
nontrivially, true also for long-range interactions in two spatial dimensions.
We, finally, find that within our fully self-consistent approach, the
fragmentation degree, to a good approximation, decreases universally as
when only is varied.Comment: 8 pages of RevTex4-1, 5 figure
Phases, many-body entropy measures and coherence of interacting bosons in optical lattices
Already a few bosons with contact interparticle interactions in small optical
lattices feature a variety of quantum phases: superfluid, Mott-insulator and
fermionized Tonks gases can be probed in such systems. To detect these phases
-- pivotal for both experiment and theory -- as well as their many-body
properties we analyze several distinct measures for the one-body and many-body
Shannon information entropies. We exemplify the connection of these entropies
with spatial correlations in the many-body state by contrasting them to the
Glauber normalized correlation functions. To obtain the ground-state for
lattices with commensurate filling (i.e. an integer number of particles per
site) for the full range of repulsive interparticle interactions we utilize the
multiconfigurational time-dependent Hartree method for bosons (MCTDHB) in order
to solve the many-boson Schr\"odinger equation. We demonstrate that all
emergent phases -- the superfluid, the Mott insulator, and the fermionized gas
can be characterized equivalently by our many-body entropy measures and by
Glauber's normalized correlation functions. In contrast to our many-body
entropy measures, single-particle entropy cannot capture these transitions.Comment: 11 pages, 7 figures, software available at http://ultracold.or
The Classical Heisenberg Model on the Centred Pyrochlore Lattice
The centred pyrochlore lattice is a novel geometrically frustrated lattice,
realized in the metal-organic framework Mn(ta) (arXiv:2203.08780) where the
basic unit of spins is a five site centred tetrahedron. Here, we present an
in-depth theoretical study of the classical Heisenberg model on this
lattice, using a combination of mean-field analytical methods and Monte Carlo
simulations. We find a rich phase diagram with low temperature states
exhibiting ferrimagnetic order, partial ordering, and a highly degenerate spin
liquid with distinct regimes of low temperature correlations. We discuss in
detail how the regime displaying broadened pinch points in its spin structure
factor is consistent with an effective description in terms of a fluid of
interacting charges. We also show how this picture holds in two dimensions on
the analogous centred kagome lattice and elucidate the connection to the
physics of thin films in () dimensions. Furthermore, we show that a
Coulomb phase can be stabilized on the centred pyrochlore lattice by the
addition of further neighbour couplings. This demonstrates the centred
pyrochlore lattice is an experimentally relevant geometry which naturally hosts
emergent gauge fields in the presence of charges at low energies.Comment: 29 pages, 9 figures, resubmission to SciPost with minor revision
Decay modes of two repulsively interacting bosons
We study the decay of two repulsively interacting bosons tunneling through a
delta potential barrier by direct numerical solution of the time-dependent
Schr\"odinger equation. The solutions are analyzed according to the regions of
particle presence: both particles inside the trap (in-in), one particle in and
one particle out (in-out), and both particles outside (out-out). It is shown
that the in-in probability is dominated by exponential decay, and its decay
rate is predicted very well from outgoing boundary conditions.
Up to a certain range of interaction strength the decay of in-out probability
is dominated by the single particle decay mode.
The decay mechanisms are adequately described by simple models.Comment: 18 pages, 13 figure
Rotating solenoidal perfect fluids of Petrov type D
We prove that aligned Petrov type D perfect fluids for which the vorticity
vector is not orthogonal to the plane of repeated principal null directions and
for which the magnetic part of the Weyl tensor with respect to the fluid
velocity has vanishing divergence, are necessarily purely electric or locally
rotationally symmetric. The LRS metrics are presented explicitly.Comment: 6 pages, no figure
Complete classification of purely magnetic, non-rotating and non-accelerating perfect fluids
Recently the class of purely magnetic non-rotating dust spacetimes has been
shown to be empty (Wylleman, Class. Quant. Grav. 23, 2727). It turns out that
purely magnetic rotating dust models are subject to severe integrability
conditions as well. One of the consequences of the present paper is that also
rotating dust cannot be purely magnetic when it is of Petrov type D or when it
has a vanishing spatial gradient of the energy density. For purely magnetic and
non-rotating perfect fluids on the other hand, which have been fully classified
earlier for Petrov type D (Lozanovski, Class. Quant. Grav. 19, 6377), the fluid
is shown to be non-accelerating if and only if the spatial density gradient
vanishes. Under these conditions, a new and algebraically general solution is
found, which is unique up to a constant rescaling, which is spatially
homogeneous of Bianchi type , has degenerate shear and is of Petrov type
I( in the extended Arianrhod-McIntosh classification.
The metric and the equation of state are explicitly constructed and
properties of the model are briefly discussed. We finally situate it within the
class of normal geodesic flows with degenerate shear tensor.Comment: 12 pages; introduction partly rewritten, notation made more clear,
table of results adde
- …