15 research outputs found
Adsorbate Electric Fields on a Cryogenic Atom Chip
We investigate the behaviour of electric fields originating from adsorbates
deposited on a cryogenic atom chip as it is cooled from room temperature to
cryogenic temperature. Using Rydberg electromagnetically induced transparency
we measure the field strength versus distance from a 1 mm square of YBCO
patterned onto a YSZ chip substrate. We find a localized and stable dipole
field at room temperature and attribute it to a saturated layer of chemically
adsorbed rubidium atoms on the YBCO. As the chip is cooled towards 83 K we
observe a change in sign of the electric field as well as a transition from a
localized to a delocalized dipole density. We relate these changes to the onset
of physisorption on the chip surface when the van der Waals attraction
overcomes the thermal desorption mechanisms. Our findings suggest that, through
careful selection of substrate materials, it may be possible to reduce the
electric fields caused by atomic adsorption on chips, opening up experiments to
controlled Rydberg-surface coupling schemes.Comment: 5 pages, 4 figure
Reconfigurable self-sufficient traps for ultracold atoms based on a superconducting square
We report on the trapping of ultracold atoms in the magnetic field formed
entirely by persistent supercurrents induced in a thin film type-II
superconducting square. The supercurrents are carried by vortices induced in
the 2D structure by applying two magnetic field pulses of varying amplitude
perpendicular to its surface. This results in a self-sufficient quadrupole trap
that does not require any externally applied fields. We investigate the
trapping parameters for different supercurrent distributions. Furthermore, to
demonstrate possible applications of these types of supercurrent traps we show
how a central quadrupole trap can be split into four traps by the use of a bias
field.Comment: 5 pages, 7 figure
Density dependence of the Ionization Avalanche in ultracold Rydberg gases
We report on the behaviour of the ionization avalanche in an ensemble of
ultracold 87Rb atoms coupled to a high lying Rydberg state and investigate
extensions to the current model by including the effects of three-body
recombination and plasma expansion. To separate the two effects we study the
time dependence of the plasma formation at various densities as well as for
different nS and nD states. At medium densities and low n we observe the onset
of the avalanche as has been reported in other experiments, as well as a
subsequent turn-off of the avalanche for longer excitation times, which we
associate with plasma expansion. At higher densities and for higher lying
Rydberg states we observe a disappearance of the avalanche signature, which we
attribute to three-body recombination.Comment: 5 pages, 4 figure
Engineering the sub-Doppler force in magneto-optical traps
Current dual-frequency magneto-optical traps (MOTs) for ultracold molecules are plagued by sub-Doppler heating effects, making them vastly inferior to standard atomic MOTs. Here we demonstrate theoretically that the sub-Doppler effects in such a MOT can be engineered to provide cooling instead of heating. We give an intuitive picture how to achieve such cooling and show the cooling and trapping force results of the 16-level optical Bloch equations for the case of CaF molecules. From three-dimensional Monte Carlo simulations we estimate the temperature and density of our MOT to be 40μK and 4×108cm-3, respectively, for a molecule number of 1×105. We also extend our idea to the case of atomic MOTs and show that it can be used to produce sub-Doppler forces in these systems that are much more robust against magnetic fields
Magnetic confinement of neutral atoms based on patterned vortex distributions in superconducting disks and rings
We propose and analyze neutral atom traps generated by vortices imprinted by
magnetic field pulse sequences in type-II superconducting disks and rings. We
compute the supercurrent distribution and magnetic field resulting from the
vortices in the superconductor. Different patterns of vortices can be written
by versatile loading field sequences. We discuss in detail procedures to
generate quadrupole traps, self-sufficient traps and ring traps based on
superconducting disks and rings. The ease of creating these traps and the low
current noise in supercurrent carrying structures makes our approach attractive
for designing atom chip interferometers and probes.Comment: 7 pages, 9 figure
Superconducting atom chips
10.1109/IQEC-CLEO.2011.61938012011 Int. Quantum Electron. Conf., IQEC 2011 and Conf. Lasers and Electro-Optics, CLEO Pacific Rim 2011 Incorporating the Australasian Conf. Optics, Lasers and Spectroscopy and the Australian Conf.907-90
A Zeeman slower for diatomic molecules
We present a novel slowing scheme for beams of laser-coolable diatomic molecules reminiscent of Zeeman slowing of atomic beams. The scheme results in efficient compression of the one-dimensional velocity distribution to velocities trappable by magnetic or magneto-optical traps. We experimentally demonstrate our method in an atomic testbed and show an enhancement of flux below v = 35 m s-1 by a factor of ≈20 compared to white light slowing. 3D Monte Carlo simulations performed to model the experiment show excellent agreement. We apply the same simulations to the prototype molecule 88Sr19F and expect 15% of the initial flux to be continuously compressed in a narrow velocity window at around 10 m s-1. This is the first experimentally shown continuous and dissipative slowing technique in molecule-like level structures, promising to provide the missing link for the preparation of large ultracold molecular ensembles. © 2018 The Author(s). Published by IOP Publishing Ltd on behalf of Deutsche Physikalische Gesellschaft
Engineering the sub-Doppler force in molecular magneto-optical traps
Current dual-frequency magneto-optical traps for ultracold molecules are
plagued by sub-Doppler heating effects, making them vastly inferior to standard
atomic MOTs. Here we demonstrate theoretically that the sub-Doppler effects in
such a MOT can be engineered to provide cooling instead of heating. We give an
intuitive picture how to achieve such cooling and show the cooling and trapping
force results of the 16 level optical Bloch equations for the case of CaF
molecules. From three-dimensional Monte Carlo simulations we estimate the
temperature and density of our MOT to be and
respectively for a molecule number of .Comment: 14 pages, 6 figure