1,059 research outputs found
Room temperature Rydberg Single Photon Source
We present an optimal protocol to implement a room temperature Rydberg single
photon source within an experimental setup based on micro cells filled with
thermal vapor. The optimization of a pulsed four wave mixing scheme allows to
double the effective Rydberg blockade radius as compared to a simple Gaussian
pulse scheme, releasing some of the constrains on the geometry of the micro
cells. The performance of the optimized protocol is improved by about 70% with
respect to the standard protocol.Comment: 5 pages, 6 figure
Observation of Feshbach resonances in an ultracold gas of Cr
We have observed Feshbach resonances in elastic collisions between ultracold
Cr atoms. This is the first observation of collisional Feshbach
resonances in an atomic species with more than one valence electron. The zero
nuclear spin of Cr and thus the absence of a Fermi-contact interaction
leads to regularly-spaced resonance sequences. By comparing resonance positions
with multi-channel scattering calculations we determine the s-wave scattering
length of the lowest potentials to be
\unit[112(14)]{a_0}, \unit[58(6)]{a_0} and -\unit[7(20)]{a_0} for S=6, 4,
and 2, respectively, where a_{0}=\unit[0.0529]{nm}.Comment: 4 pages, 2 figures, 1 tabl
Expansion dynamics of a dipolar Bose-Einstein condensate
Our recent measurements on the expansion of a chromium dipolar condensate
after release from an optical trapping potential are in good agreement with an
exact solution of the hydrodynamic equations for dipolar Bose gases. We report
here the theoretical method used to interpret the measurement data as well as
more details of the experiment and its analysis. The theory reported here is a
tool for the investigation of different dynamical situations in time-dependent
harmonic traps.Comment: 12 pages. Submitted to PR
Depolarisation cooling of an atomic cloud
We propose a cooling scheme based on depolarisation of a polarised cloud of
trapped atoms. Similar to adiabatic demagnetisation, we suggest to use the
coupling between the internal spin reservoir of the cloud and the external
kinetic reservoir via dipolar relaxation to reduce the temperature of the
cloud. By optical pumping one can cool the spin reservoir and force the cooling
process. In case of a trapped gas of dipolar chromium atoms, we show that this
cooling technique can be performed continuously and used to approach the
critical phase space density for BECComment: 8 pages, 5 figure
Cascade of magnetic field induced Lifshitz transitions in the ferromagnetic Kondo lattice material YbNi4P2
A ferromagnetic quantum critical point is thought not to exist in two and
three-dimensional metallic systems yet is realized in the Kondo lattice
compound YbNi4(P,As)2, possibly due to its one-dimensionality. It is crucial to
investigate the dimensionality of the Fermi surface of YbNi4P2 experimentally
but common probes such as ARPES and quantum oscillation measurements are
lacking. Here, we studied the magnetic field dependence of transport and
thermodynamic properties of YbNi4P2. The Kondo effect is continuously
suppressed and additionally we identify nine Lifshitz transitions between 0.4
and 18 T. We analyze the transport coefficients in detail and identify the type
of Lifshitz transitions as neck or void type to gain information on the Fermi
surface of YbNi4P2. The large number of Lifshitz transitions observed within
this small energy window is unprecedented and results from the particular flat
renormalized band structure with strong 4f-electron character shaped by the
Kondo lattice effect.Comment: 6 pages, 4 figure
Determination of the s-wave Scattering Length of Chromium
We have measured the deca-triplet s-wave scattering length of the bosonic
chromium isotopes Cr and Cr. From the time constants for
cross-dimensional thermalization in atomic samples we have determined the
magnitudes and ,
where . By measuring the rethermalization rate of Cr over a
wide temperature range and comparing the temperature dependence with the
effective-range theory and single-channel calculations, we have obtained strong
evidence that the sign of is positive. Rescaling our Cr
model potential to Cr strongly suggests that is positive,
too.Comment: v3: corrected typo in y-axis scaling of Figs. 3 and
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