62 research outputs found
Quantum dynamics of repulsively bound atom pairs in the Bose-Hubbard model
We investigate the quantum dynamics of repulsively bound atom pairs in an
optical lattice described by the periodic Bose-Hubbard model both analytically
and numerically. In the strongly repulsive limit, we analytically study the
dynamical problem by the perturbation method with the hopping terms treated as
a perturbation. For a finite-size system, we numerically solve the dynamic
problem in the whole regime of interaction by the exact diagonalization method.
Our results show that the initially prepared atom pairs are dynamically stable
and the dissociation of atom pairs is greatly suppressed when the strength of
the on-site interaction is much greater than the tunneling amplitude, i.e., the
strongly repulsive interaction induces a self-localization phenomenon of the
atom pairs.Comment: 7 pages, 6 figures, significant changes mad
Preparation of stable excited states in an optical lattice via sudden quantum quench
We study how stable excited many-body states of the Bose-Hubbard model,
including both the gas-like state for strongly attractive bosons and bound
cluster state for repulsive bosons, can be produced with cold bosonic atoms in
an one-dimensional optical lattice. Starting from the initial ground states of
strongly interacting bosonic systems, we can achieve stable excited states of
the systems with opposite interaction strength by suddenly switching the
interaction to the opposite limit. By exactly solving dynamics of the
Bose-Hubbard model, we demonstrate that the produced excited state can be a
very stable dynamic state. This allows the experimental study of excited state
properties of ultracold atoms system in optical lattices.Comment: 5 pages, 4 figure
-body Correlation of Tonks-Girardeau Gas
For the well-known exponential complexity it is a giant challenge to
calculate the correlation function for general many-body wave function. We
investigate the ground state th-order correlation functions of the
Tonks-Girardeau (TG) gases. Basing on the wavefunction of free fermions and
Bose-Fermi mapping method we obtain the exact ground state wavefunction of TG
gases. Utilizing the properties of Vandermonde determinant and Toeplitz matrix,
the th-order correlation function is formulated as -order Toeplitz
determinant, whose element is the integral dependent on 2 sign functions
and can be computed analytically. By reducing the integral on domain
into the summation of the integral on several independent domains, we obtain
the explicit form of the Toeplitz matrix element ultimately. As the
applications we deduce the concise formula of the reduced two-body density
matrix and discuss its properties. The corresponding natural orbitals and their
occupation distribution are plotted. Furthermore, we give a concise formula of
the reduced three-body density matrix and discuss its properties. It is shown
that in the successive second measurements, atoms appear in the regions where
atoms populate with the maximum probability in the first measurement.Comment: 8 pages, 7 figure
Corrigendum: Therapy of spinal cord injury by folic acid polyethylene glycol amine-modified zeolitic imidazole framework-8 nanoparticles targeted activated M/Ms
Chaos signatures of current phase transition in a toroidal trap
In this work we demonstrate how the directed motion of atomic Bose-Einstein
condensates in a toroidal trap can be controlled by applying a zero-mean
oscillatory driving field. We show that due to the self-trapping effect in
momentum space, the oscillatory amplitude of the current can be significantly
suppressed and a nearly constant directed current can be obtained preserving
the initial current values, by decreasing the driving amplitude, even when the
atomic interactions are relatively small. We also reveal numerically the
mean-field chaos can serve as an indicator of a quantum phase transition
between the vanishing current regime and nonvanishing current regime. Our
results are corroborated by an effective three-mode model, which provides an
excellent account of the ratchet dynamics of the system.Comment: 7 pages, 9 figure
Intrinsic relation between ground-state fidelity and the characterization of a quantum phase transition
The notion of fidelity in quantum information science has been recently
applied to analyze quantum phase transitions from the viewpoint of the ground
state (GS) overlap for various many-body systems. In this work, we unveil the
intrinsic relation between the GS fidelity and the derivatives of GS energy and
find that they play equivalent role in identifying the quantum phase
transition. The general connection between the two approaches enables us to
understand the different singularity and scaling behaviors of fidelity
exhibited in various systems on general grounds. Our general conclusions are
illustrated via several quantum spin models which exhibit different kinds of
QPTs.Comment: 5 pages, 3 figure
Comparative genomics reveals the hybrid origin of a macaque group
Although species can arise through hybridization, compelling evidence for hybrid speciation has been reported only rarely in animals. Here, we present phylogenomic analyses on genomes from 12 macaque species and show that the fascicularis group originated from an ancient hybridization between the sinica and silenus groups ~3.45 to 3.56 million years ago. The X chromosomes and low-recombination regions exhibited equal contributions from each parental lineage, suggesting that they were less affected by subsequent backcrossing and hence could have played an important role in maintaining hybrid integrity. We identified many reproduction-associated genes that could have contributed to the development of the mixed sexual phenotypes characteristic of the fascicularis group. The phylogeny within the silenus group was also resolved, and functional experimentation confirmed that all extant Western silenus species are susceptible to HIV-1 infection. Our study provides novel insights into macaque evolution and reveals a hybrid speciation event that has occurred only very rarely in primates
Tem observation and fracture morphology in the cghaz of a new 0cr18mo2ti ferritic stainless steel
Fine structure in the inter-critical heat-affected zone of HQ130 super-high strength steel
- …