61 research outputs found
Density wave and supersolid phases of correlated bosons in an optical lattice
Motivated by the recent experiment on the Bose-Einstein condensation of
Cr atoms with long-range dipolar interactions (Werner J. et al., Phys.
Rev. Lett., 94 (2005) 183201), we consider a system of bosons with repulsive
nearest and next-nearest neighbor interactions in an optical lattice. The
ground state phase diagram, calculated using the Gutzwiller ansatz, shows,
apart from the superfluid (SF) and the Mott insulator (MI), two modulated
phases, \textit{i.e.}, the charge density wave (CDW) and the supersolid (SS).
Excitation spectra are also calculated which show a gap in the insulators,
gapless, phonon mode in the superfluid and the supersolid, and a mode softening
of superfluid excitations in the vicinity of the modulated phases. We discuss
the possibility of observing these phases in cold dipolar atoms and propose
experiments to detect them
Collective Excitations of Bose-Einstein Condensates in a Double-Well Potential
We investigate collective excitations of Bose-Einstein condensates at
absolute zero in a double-well trap. We solve the Bogoliubov equations with a
double-well trap, and show that the crossover from the dipole mode to the
Josephson plasma mode occurs in the lowest energy excitation. It is found that
the anomalous tunneling property of low energy excitations is crucial to the
crossover.Comment: 14 pages, 6 figure
Ultracold Dipolar Gases in Optical Lattices
This tutorial is a theoretical work, in which we study the physics of
ultra-cold dipolar bosonic gases in optical lattices. Such gases consist of
bosonic atoms or molecules that interact via dipolar forces, and that are
cooled below the quantum degeneracy temperature, typically in the nK range.
When such a degenerate quantum gas is loaded into an optical lattice produced
by standing waves of laser light, new kinds of physical phenomena occur. These
systems realize then extended Hubbard-type models, and can be brought to a
strongly correlated regime. The physical properties of such gases, dominated by
the long-range, anisotropic dipole-dipole interactions, are discussed using the
mean-field approximations, and exact Quantum Monte Carlo techniques (the Worm
algorithm).Comment: 56 pages, 26 figure
Signature of anyonic statistics in the integer quantum Hall regime
Anyons are exotic low-dimensional quasiparticles whose unconventional quantum
statistics extends the binary particle division into fermions and bosons. The
fractional quantum Hall regime provides a natural host, with first convincing
anyon signatures recently observed through interferometry and
cross-correlations of colliding beams. However, the fractional regime is rife
with experimental complications, such as an anomalous tunneling density of
states, which impede the manipulation of anyons. Here we show experimentally
that the canonical integer quantum Hall regime can provide a robust anyon
platform. Exploiting the Coulomb interaction between two co-propagating quantum
Hall channels, an electron injected into one channel splits into two fractional
charges behaving as abelian anyons. Their unconventional statistics is revealed
by negative cross-correlations between dilute quasiparticle beams. Similarly to
fractional quantum Hall observations, we show that the negative signal stems
from a time-domain braiding process, here involving the incident fractional
quasiparticles and spontaneously generated electron-hole pairs. Beyond the
dilute limit, a theoretical understanding is achieved via the edge
magnetoplasmon description of interacting integer quantum Hall channels. Our
findings establish that, counter-intuitively, the integer quantum Hall regime
provides a platform of choice for exploring and manipulating quasiparticles
with fractional quantum statistics.Comment: 6 pages, 4 figures, 4 Extended Data figures, Methods, Supplemental
Informatio
Measurement of hadron cross sections with the SND detector
New results on exclusive hadron production in annihilation obtained
in experiments with the SND detector at the VEPP-2M and VEPP-2000
colliders are presented.Comment: 4 pages, 4 figures, presented at the 14th International Workshop on
Meson Production, Properties and Interaction (MESON 2016), Cracow, Poland,
2nd - 7th June 201
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