1,805 research outputs found
Lorentz Transformations as Lie-Poisson Symmetries
We write down the Poisson structure for a relativistic particle where the
Lorentz group does not act canonically, but instead as a Poisson-Lie group. In
so doing we obtain the classical limit of a particle moving on a noncommutative
space possessing invariance. We show that if the standard mass
shell constraint is chosen for the Hamiltonian function, then the particle
interacts with the space-time. We solve for the trajectory and find that it
originates and terminates at singularities.Comment: 18 page
Surface-acoustic-wave driven planar light-emitting device
Electroluminescence emission controlled by means of surface acoustic waves
(SAWs) in planar light-emitting diodes (pLEDs) is demonstrated. Interdigital
transducers for SAW generation were integrated onto pLEDs fabricated following
the scheme which we have recently developed. Current-voltage, light-voltage and
photoluminescence characteristics are presented at cryogenic temperatures. We
argue that this scheme represents a valuable building block for advanced
optoelectronic architectures
Accurate near-threshold model for ultracold KRb dimers from interisotope Feshbach spectroscopy
We investigate magnetic Feshbach resonances in two different ultracold K-Rb
mixtures. Information on the K(39)-Rb(87) isotopic pair is combined with novel
and pre-existing observations of resonance patterns for K(40)-Rb(87).
Interisotope resonance spectroscopy improves significantly our near-threshold
model for scattering and bound-state calculations. Our analysis determines the
number of bound states in singlet/triplet potentials and establishes precisely
near threshold parameters for all K-Rb pairs of interest for experiments with
both atoms and molecules. In addition, the model verifies the validity of the
Born-Oppenheimer approximation at the present level of accuracy.Comment: 9 pages, 7 figure
Acoustic charge transport in n-i-n three terminal device
We present an unconventional approach to realize acoustic charge transport
devices that takes advantage from an original input region geometry in place of
standard Ohmic input contacts. Our scheme is based on a n-i-n lateral junction
as electron injector, an etched intrinsic channel, a standard Ohmic output
contact and a pair of in-plane gates. We show that surface acoustic waves are
able to pick up electrons from a current flowing through the n-i-n junction and
steer them toward the output contact. Acoustic charge transport was studied as
a function of the injector current and bias, the SAW power and at various
temperatures. The possibility to modulate the acoustoelectric current by means
of lateral in-plane gates is also discussed. The main advantage of our approach
relies on the possibility to drive the n-i-n injector by means of both voltage
or current sources, thus allowing to sample and process voltage and current
signals as well.Comment: 9 pages, 3 figures. Submitted to Applied Physics Letter
Collisional and molecular spectroscopy in an ultracold Bose-Bose mixture
The route toward a Bose-Einstein condensate of dipolar molecules requires the
ability to efficiently associate dimers of different chemical species and
transfer them to the stable rovibrational ground state. Here, we report on
recent spectroscopic measurements of two weakly bound molecular levels and
newly observed narrow d-wave Feshbach resonances. The data are used to improve
the collisional model for the Bose-Bose mixture 41K87Rb, among the most
promising candidates to create a molecular dipolar BEC.Comment: 13 pages, 3 figure
Optimisation of accurate rutile (110), (100), (101) and (001) surface models from periodic DFT calculations
In this paper, geometric bulk parameters, bulk moduli, energy gaps and relative stabilities of the TiO2 anatase and rutile phases were determined from periodic DFT calculations. Then, for the rutile phase, structures, relaxations and surface energies of the (110), (100), (101) and (001) faces were computed. The calculated surface energies are consistent with the natural rutile powder composition, even if a dependence on the number of layers of the slab used to model the surface was identified. Internal constraints, consisting in freezing some internal layers of the slab to atomic bulk positions, were thus added to mimic the bulk hardness in order to stabilise the computed surface energies for thinner systems. In parallel, the influence of pseudopotentials was studied and it appears that four valence electrons for titanium atoms are sufficient. The aim of this study was to optimise accurate rutile TiO2 surface models that will be used in further calculations to investigate water and uranyl ion sorption mechanisms
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
Search for dark matter signals towards a selection of recently detected DES dwarf galaxy satellites of the Milky Way with H.E.S.S.
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