3,453 research outputs found
Quantum knots in Bose-Einstein condensates created by counterdiabatic control
We theoretically study the creation of knot structures in the polar phase of
spin-1 BECs using the counterdiabatic protocol in an unusual fashion. We
provide an analytic solution to the evolution of the external magnetic field
that is used to imprint the knots. As confirmed by our simulations using the
full three-dimensional spin-1 Gross-Pitaevskii equation, our method allows for
the precise control of the Hopf charge as well as the creation time of the
knots. The knots with Hopf charge exceeding unity display multiple nested Hopf
links.Comment: 7 pages, 6 figure
Spin-dependent Polarizability of Nucleon with Dispersion Relation in the Skyrme Model
We calculate the spin-dependent polarizability of the nucleon in the Skyrme
model. The result is compared with that of a heavy baryon chiral perturbation
theory(HBChPT), and is shown to be the same as that of HBChPT up to the
-pole terms in the narrow width limit of the state and with
the experimental physical constants. The effect of the channel is
rather small and is numerically quite similar to that of the loop in
the HBChPT. The electric and magnetic polarizabilities are recalculated using
the transverse photon and a consistent inclusion of the width.Comment: 11 pages, LaTeX, no figures. misprints correcte
Zero Landau level in folded graphene nanoribbons
Graphene nanoribbons can be folded into a double layer system keeping the two
layers decoupled. In the Quantum Hall regime folds behave as a new type of Hall
bar edge. We show that the symmetry properties of the zero Landau level in
metallic nanoribbons dictate that the zero energy edge states traversing a fold
are perfectly transmitted onto the opposite layer. This result is valid
irrespective of fold geometry, magnetic field strength and crystallographic
orientation of the nanoribbon. Backscattering suppression on the N=0 Hall
plateau is ultimately due to the orthogonality of forward and backward
channels, much like in the Klein paradox.Comment: Final published version, with supplementary material appendi
Majorana Fermions and Non-Abelian Statistics in Three Dimensions
We show that three dimensional superconductors, described within a Bogoliubov
de Gennes framework can have zero energy bound states associated with pointlike
topological defects. The Majorana fermions associated with these modes have
non-Abelian exchange statistics, despite the fact that the braid group is
trivial in three dimensions. This can occur because the defects are associated
with an orientation that can undergo topologically nontrivial rotations. A new
feature of three dimensional systems is that there are "braidless" operations
in which it is possible to manipulate the groundstate associated with a set of
defects without moving or measuring them. To illustrate these effects we
analyze specific architectures involving topological insulators and
superconductors.Comment: 4 pages, 2 figures, published versio
Dynamically stable multiply quantized vortices in dilute Bose-Einstein condensates
Multiquantum vortices in dilute atomic Bose-Einstein condensates confined in
long cigar-shaped traps are known to be both energetically and dynamically
unstable. They tend to split into single-quantum vortices even in the ultralow
temperature limit with vanishingly weak dissipation, which has also been
confirmed in the recent experiments [Y. Shin et al., Phys. Rev. Lett. 93,
160406 (2004)] utilizing the so-called topological phase engineering method to
create multiquantum vortices. We study the stability properties of multiquantum
vortices in different trap geometries by solving the Bogoliubov excitation
spectra for such states. We find that there are regions in the trap asymmetry
and condensate interaction strength plane in which the splitting instability of
multiquantum vortices is suppressed, and hence they are dynamically stable. For
example, the doubly quantized vortex can be made dynamically stable even in
spherical traps within a wide range of interaction strength values. We expect
that this suppression of vortex-splitting instability can be experimentally
verified.Comment: 5 pages, 6 figure
Imprinting the memory into paste and its visualization as crack patterns in drying process
In the drying process of paste, we can imprint into the paste the order how
it should be broken in the future. That is, if we vibrate the paste before it
is dried, it remembers the direction of the initial external vibration, and the
morphology of resultant crack patterns is determined solely by the memory of
the direction. The morphological phase diagram of crack patterns and the
rheological measurement of the paste show that this memory effect is induced by
the plasticity of paste.Comment: 4 pages, 3 figures, submitted to JPS
Geometric phase contribution to quantum non-equilibrium many-body dynamics
We study the influence of geometry of quantum systems underlying space of
states on its quantum many-body dynamics. We observe an interplay between
dynamical and topological ingredients of quantum non-equilibrium dynamics
revealed by the geometrical structure of the quantum space of states. As a
primary example we use the anisotropic XY ring in a transverse magnetic field
with an additional time-dependent flux. In particular, if the flux insertion is
slow, non-adiabatic transitions in the dynamics are dominated by the dynamical
phase. In the opposite limit geometric phase strongly affects transition
probabilities. We show that this interplay can lead to a non-equilibrium phase
transition between these two regimes. We also analyze the effect of geometric
phase on defect generation during crossing a quantum critical point.Comment: 4 pages, 3 figures. Added an appendix with supplementary informatio
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