1,514 research outputs found
Resonant coupling of a Bose-Einstein condensate to a micromechanical oscillator
We report experiments in which the vibrations of a micromechanical oscillator
are coupled to the motion of Bose-condensed atoms in a trap. The interaction
relies on surface forces experienced by the atoms at about one micrometer
distance from the mechanical structure. We observe resonant coupling to several
well-resolved mechanical modes of the condensate. Coupling via surface forces
does not require magnets, electrodes, or mirrors on the oscillator and could
thus be employed to couple atoms to molecular-scale oscillators such as carbon
nanotubes.Comment: 9 pages, 4 figure
ICP polishing of silicon for high quality optical resonators on a chip
Miniature concave hollows, made by wet etching silicon through a circular
mask, can be used as mirror substrates for building optical micro-cavities on a
chip. In this paper we investigate how ICP polishing improves both shape and
roughness of the mirror substrates. We characterise the evolution of the
surfaces during the ICP polishing using white-light optical profilometry and
atomic force microscopy. A surface roughness of 1 nm is reached, which reduces
to 0.5 nm after coating with a high reflectivity dielectric. With such smooth
mirrors, the optical cavity finesse is now limited by the shape of the
underlying mirror
Self-localization of magnon Bose-Einstein condensates in the ground state and on excited levels: from harmonic to box-like trapping potential
Long-lived coherent spin precession of 3He-B at low temperatures around 0.2
Tc is a manifestation of Bose-Einstein condensation of spin-wave excitations or
magnons in a magnetic trap which is formed by the order-parameter texture and
can be manipulated experimentally. When the number of magnons increases, the
orbital texture reorients under the influence of the spin-orbit interaction and
the profile of the trap gradually changes from harmonic to a square well, with
walls almost impenetrable to magnons. This is the first experimental example of
Bose condensation in a box. By selective rf pumping the trap can be populated
with a ground-state condensate or one at any of the excited energy levels. In
the latter case the ground state is simultaneously populated by relaxation from
the exited level, forming a system of two coexisting condensates.Comment: 4 pages, 5 figure
Correction to: Economic evaluation of AbobotulinumtoxinA vs OnabotulinumtoxinA in real-life clinical management of cervical dystonia.
[This corrects the article DOI: 10.1186/s40734-020-0083-0.]
Probing Water State during Lipidic Mesophases Phase Transitions
We investigate the static and dynamic states of water network during the phase transitions from double gyroid ((Formula presented.)) to double diamond ((Formula presented.)) bicontinuous cubic phases and from the latter to the reverse hexagonal (HII) phase in monolinolein based lipidic mesophases by combining FTIR and broadband dielectric spectroscopy (BDS). In both cubic(s) and HII phase, two dynamically different fractions of water are detected and attributed to bound and interstitial free water. The dynamics of the two water fractions are all slower than bulk water due to the hydrogen-bonds between water molecules and the lipid's polar headgroups and to nanoconfinement. Both FTIR and BDS results suggest that a larger fraction of water is hydrogen-bonded to the headgroup of lipids in the HII phase at higher temperature than in the cubic phase at lower temperature via H-bonds, which is different from the common expectation that the number of H-bonds should decrease with increase of temperature. These findings are rationalized by considering the topological ratio of interface/volume of the two mesophases.ISSN:1433-7851ISSN:1521-3773ISSN:0570-083
CuAu-type ordering in epitaxial CuInS<sub>2</sub> films
Ordering of Cu and In atoms in near-stoichiometric CuInS2 epitaxial films grown on Si (111) by molecular beam epitaxy was studied by transmission electron microscopy. Nonchalcopyrite ordering of the metal atoms in CuInS2 is observed, which is identified as CuAu-type ordering. Sharp spots in electron diffraction patterns reveal the ordered Cu and In atom planes alternating along the [001] direction over a long range. High-resolution electron microscopy confirms this ordering. The CuAu-ordered structure coexists with the chalcopyrite ordered structure, in agreement with theoretical prediction
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