47,965 research outputs found
Mesoscopic ensembles of polar bosons in triple-well potentials
Mesoscopic dipolar Bose gases in triple-well potentials offer a minimal
system for the analysis of the long-range character of the dipole-dipole
interactions. We show that this long-range character may be clearly revealed by
a variety of possible ground-state phases. In addition, an appropriate control
of short-range and dipolar interactions may lead to novel scenarios for the
dynamics of atoms and polar molecules in lattices, including the dynamical
creation of mesoscopic Schr\"odinger cats, which may be employed as a source of
highly-nonclassical states for Heisenberg-limited interferometry.Comment: 4 pages, 3 figures. Identical to the published version, including
supplemental material (4 pages, 6 figures)
Plasmonics in topological insulators: Spin-charge separation, the influence of the inversion layer, and phonon-plasmon coupling
We demonstrate via three examples that topological insulators (TI) offer a
new platform for plasmonics. First, we show that the collective excitations of
a thin slab of a TI display spin-charge separation. This gives rise to purely
charge-like optical and purely spin-like acoustic plasmons, respectively.
Second, we argue that the depletion layer mixes Dirac and Schr\"odinger
electrons which can lead to novel features such as high modulation depths and
interband plasmons. The analysis is based on an extension of the usual formula
for optical plasmons that depends on the slab width and on the dielectric
constant of the TI. Third, we discuss the coupling of the TI surface phonons to
the plasmons and find strong hybridisation especially for samples with large
slab widths.Comment: 37 pages, 7 figure
Spin-charge separation of plasmonic excitations in thin topological insulators
We discuss plasmonic excitations in a thin slab of a topological insulators.
In the limit of no hybridization of the surface states and same electronic
density of the two layers, the electrostatic coupling between the top and
bottom layers leads to optical and acoustic plasmons which are purely charge
and spin collective oscillations. We then argue that a recent experiment on the
plasmonic excitations of Bi2Se3 [Di Pietro et al, Nat. Nanotechnol. 8, 556
(2013)] must be explained by including the charge response of the
two-dimensional electron gas of the depletion layer underneath the two
surfaces. We also present an analytic formula to fit their data.Comment: 7 pages, 5 figure
Collective oscillations of dipolar Bose-Einstein condensates and accurate comparison between contact and dipolar interaction
We propose a scheme for the measurement of the s-wave scattering length
of an atom or molecule with significant dipole-dipole interaction with an
accuracy at the percent level. The frequencies of the collective oscillations
of a Bose-Einstein condensate are shifted by the magnetic dipole interaction.
The shift is polarization dependent and proportional to the ratio
of dipolar and s-wave coupling constants. Measuring the
differences in the frequencies for different polarization we can extract the
value of and thus measure . We calculate the frequency
shifts for a large variety of non-axisymmetric harmonic traps in the
Thomas-Fermi limit and find optimal trapping geometries to maximize the shifts.Comment: 4 pages, brief repor
Spin-3 Chromium Bose-Einstein Condensates
We analyze the physics of spin-3 Bose-Einstein condensates, and in particular
the new physics expected in on-going experiments with condensates of Chromium
atoms. We first discuss the ground-state properties, which, depending on still
unknown Chromium parameters, and for low magnetic fields can present various
types of phases. We also discuss the spinor-dynamics in Chromium spinor
condensates, which present significant qualitative differences when compared to
other spinor condensates. In particular, dipole-induced spin relaxation may
lead for low magnetic fields to transfer of spin into angular momentum similar
to the well-known Einstein-de Haas effect. Additionally, a rapid large
transference of population between distant magnetic states becomes also
possible.Comment: 4 pages, 3 eps figures. Error in the previous version correcte
Ultra-cold bosons in zig-zag optical lattices
Ultra-cold bosons in zig-zag optical lattices present a rich physics due to
the interplay between frustration, induced by lattice geometry, two-body
interaction and three-body constraint. Unconstrained bosons may develop chiral
superfluidity and a Mott-insulator even at vanishingly small interactions.
Bosons with a three-body constraint allow for a Haldane-insulator phase in
non-polar gases, as well as pair-superfluidity and density wave phases for
attractive interactions. These phases may be created and detected within the
current state of the art techniques.Comment: 8 pages, 9 figure
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