13,229 research outputs found
Dirac and topological phonons with spin-orbital entangled orders
We propose to study novel quantum phases and excitations for a 2D spin-orbit
(SO) coupled bosonic -orbital optical lattice based on the recent
experiments. The orbital and spin degrees of freedom with SO coupling compete
and bring about nontrivial interacting quantum effects. We develop a
self-consistent method for bosons and predict a spin-orbital entangled order
for the ground phase, in sharp contrast to spinless high-orbital systems.
Furthermore, we investigate the Bogoliubov excitations, showing that the Dirac
and topological phonons are obtained corresponding to the predicted different
spin-orbital orders. In particular, the topological phonons exhibit a bulk gap
which can be several times larger than the single-particle gap of -bands,
reflecting the enhancement of topological effect by interaction. Our results
highlight the rich physics predicted in SO coupled high-orbital systems and
shall attract experimental efforts in the future.Comment: 5 pages, 4 figures, and Supplementary Material. Figures are updated,
and some description is update
A Scaling Behavior of Bloch Oscillation in Weyl Semimetals
We predict a linear logarithmical scaling law of Bloch oscillation dynamics
in Weyl semimetals (WSMs), which can be applied to detect Weyl nodal points.
Applying the semiclassical dynamics for quasiparticles which are accelerated
bypassing a Weyl point, we show that transverse drift exhibits asymptotically a
linear log-log relation with respect to the minimal momentum measured from the
Weyl point. This linear scaling behavior is a consequence of the monopole
structure nearby the Weyl points, thus providing a direct measurement of the
topological nodal points, with the chirality and anisotropy being precisely
determined. We apply the present results to two lattice models for WSMs which
can be realized with cold atoms in experiment, and propose realistic schemes
for the experimental detection. With the analytic and numerical results we show
the feasibility of identifying topological Weyl nodal points based on the
present prediction.Comment: 5+ pages, 4 figure
Enhanced magneto-optical response due to the flat band in nanoribbons made from the lattice
We study the optical response of nanoribbons made from the
lattice under a weak magnetic field in the terahertz to far-infrared regime. It
is found that the magnetic field can open a gap in the band structure and
induce a new absorption peak with much reduced frequency in metallic armchair
ribbons and a class of zigzag ribbons with particular boundaries. This tunable
magneto-optical modulation effect is attributed to the interband transitions
between the flat band and the propagating bands. By contrast, this magnetic
modulation of gap opening and optical conductance is much weaker in metallic
armchair graphene ribbons (the case of ) in which the flat band is
absent. The enhancement in the model is analytically investigated
and explained within the perturbation theory for metallic armchair ribbons. The
magnetic field induced valley degeneracy lifting and valley splitting of the
absorption peak are also discussed in the case of zigzag ribbons. These
findings pave the way for magneto-optics devices based on the
model materials.Comment: 7 pages, 7 figures; accepted by Physical Review
Generating nonclassical photon-states via longitudinal couplings between superconducting qubits and microwave fields
Besides the conventional transverse couplings between superconducting qubits
(SQs) and electromagnetic fields, there are additional longitudinal couplings
when the inversion symmetry of the potential energies of the SQs is broken. We
study nonclassical-state generation in a SQ which is driven by a classical
field and coupled to a single-mode microwave field. We find that the classical
field can induce transitions between two energy levels of the SQs, which either
generate or annihilate, in a controllable way, different photon numbers of the
cavity field. The effective Hamiltonians of these classical-field-assisted
multiphoton processes of the single-mode cavity field are very similar to those
for cold ions, confined to a coaxial RF-ion trap and driven by a classical
field. We show that arbitrary superpositions of Fock states can be more
efficiently generated using these controllable multiphoton transitions, in
contrast to the single-photon resonant transition when there is only a SQ-field
transverse coupling. The experimental feasibility for different SQs is also
discussed.Comment: 15 pages, 8 figure
Human migration patterns in large scale spatial with the resume data
Researches on the human mobility have made great progress in many aspects,
but the long-term and long-distance migration behavior is lack of in-depth and
extensive research because of the difficult in accessing to household data. In
this paper, we use the resume data to discover the human migration behavior on
the large scale scope. It is found that the asymmetry in the flow structure
which reflects the influence of population competition is caused by the
difference of attractiveness among cities. This flow structure can be
approximately described by the gravity model of spatial economics. Besides, the
value of scaling exponent of distance function in the gravity model is less
than the value of short-term travel behavior. It means that, compared with the
short-term travel behavior, the long-term human migration behavior is less
sensitive. Moreover, the scaling coefficients of each variable in the gravity
model are investigated. The result shows that the economic level is a mainly
factor on the migration
Entangled state engineering of vibrational modes in a multi-membrane optomechanical system
We propose a method to generate entangled states of the vibrational modes of
N membranes which are coupled to a cavity mode via the radiation pressure.
Using sideband excitations, we show that arbitrary entangled states of
vibrational modes of different membranes can be produced in principle by
sequentially applying a series of classical pulses with desired frequencies,
phases and durations. As examples, we show how to synthesize several typical
entangled states, for example, Bell states, NOON states, GHZ states and W
states. The environmental effect, information leakage, and experimental
feasibility are briefly discussed. Our proposal can also be applied to other
experimental setups of optomechanical systems, in which many mechanical
resonators are coupled to a common sing-mode cavity field via the radiation
pressure.Comment: 15 pages, 10 figure
and the New Resonances and Observed by the BES Collaboration
We calculate the decay widths of both the second and the third radial
excitations of and within the framework of model. After
comparing the theoretical decay widths and decay patterns with the available
experimental data of , , and , we find
that the interpretation of and as the second radial
excitation of and crucially depends on the measured mass and
width of , which is still controversial experimentally. We suggest
that there may be sizable content in . and
can not be understood as the third radial excitations of and
, probably is a mixture of and glueball.Comment: 20 pages, 6 figure
Bifurcation and Global Dynamical Behavior of the Theory
Usually, in order to investigate the evolution of a theory, one may find the
critical points of the system and then perform perturbations around these
critical points to see whether they are stable or not. This local method is
very useful when the initial values of the dynamical variables are not far away
from the critical points. Essentially, the nonlinear effects are totally
neglected in such kind of approach. Therefore, one can not tell whether the
dynamical system will evolute to the stable critical points or not when the
initial values of the variables do not close enough to these critical points.
Furthermore, when there are two or more stable critical points in the system,
local analysis can not provide the informations that which one the system will
finally evolute to. In this paper, we have further developed the nullcline
method to study the bifurcation phenomenon and global dynamical behaviour of
the theory. We overcome the shortcoming of local analysis. And it is
very clear to see the evolution of the system under any initial conditions.Comment: 17pages, 9figure
Kerr-Sen Black Hole as Accelerator for Spinning Particles
It has been proved that arbitrarily high-energy collision between two
particles can occur near the horizon of an extremal Kerr black hole as long as
the energy and angular momentum of one particle satisfies a critical
relation, which is called the BSW mechanism. Previous researchers mainly
concentrate on geodesic motion of particles. In this paper, we will take
spinning particle which won't move along a timelike geodesic into our
consideration, hence, another parameter describing the particle's spin
angular momentum was introduced. By employing the Mathisson-Papapetrou-Dixon
equation describing the movement of spinning particle, we will explore whether
a Kerr-Sen black hole which is slightly different from Kerr black hole can be
used to accelerate a spinning particle to arbitrarily high energy. We found
that when one of the two colliding particles satisfies a critical relation
between the energy and the total angular momentum , or has a critical
spinning angular momentum , a divergence of the center-of-mass energy
will be obtained.Comment: Latex,17 pages,1 figure,minor revision,accepted by PR
Magnetic and Magnetocaloric Study of the Ferromagnetically Coupled GdF3: The Best Cryogenic Magnetic Coolant Ever
The magnetic susceptibility and isothermal magnetization for GdF3 were
measured, and the isothermal entropy change was evaluated up to 9 T. Combining
the large isotropic spin of Gd3+, the dense structure and the weak
ferromagnetic interaction, an extremely large -(delta)Sm for GdF3 was observed
up to 528 mJ cm-3 K-1 for (delta)H = 9 T, proving itself to be the best
cryogenic magnetic coolant ever.Comment: 4 Pages, 5 Figures, 1 Tabl
- …