32 research outputs found
Narrow-line magneto-optical trap for erbium
We report on the experimental realization of a robust and efficient
magneto-optical trap for erbium atoms, based on a narrow cooling transition at
583nm. We observe up to atoms at a temperature of about
. This simple scheme provides better starting conditions for direct
loading of dipole traps as compared to approaches based on the strong cooling
transition alone, or on a combination of a strong and a narrow kHz transition.
Our results on Er point to a general, simple and efficient approach to laser
cool samples of other lanthanide atoms (Ho, Dy, and Tm) for the production of
quantum-degenerate samples
NbS: A unique quasi one-dimensional conductor with three charge density wave transitions
Through transport, compositional and structural studies, we review the
features of the charge-density wave (CDW) conductor of NbS (phase II). We
highlight three central results: 1) In addition to the previously reported CDW
transitions at = 360\,K and = 150\,K, another CDW transition
occurs at a much higher temperature = 620-650\,K; evidence for the
non-linear conductivity of this CDW is presented. 2) We show that CDW
associated with the - transition arises from S vacancies acting as
donors. Such a CDW transition has not been observed before. 3) We show
exceptional coherence of the -CDW at room-temperature. Additionally, we
report on the effects of uniaxial strain on the CDW transition temperatures and
transport.Comment: 16 pages, 18 figure
Charge density wave ordering in NbSe3: possible models and the experimental evidence
Charge density wave (CDW) ordering in the prototypical low-dimensional
compound NbSe3 is reconsidered. We show that the widely accepted CDW model with
two incommensurate modulations, q1 = (0,0.241,0) and q2 = (0.5,0.260,0.5),
localized on type-III and type-I bi-capped trigonal prismatic (BCTP) columns,
does not explain some details, revealed by various microscopic methods. The
suggested alternative explanation is in a better accord with the entire
experimental evidence, including low-temperature (LT) scanning tunneling
microscopy (STM) results. It is based on the existence of modulated layered
nano-domains formed below both CDW onset temperatures. According to this model,
two of the three slightly different BCTP types of columns are modulated by the
same wave vector, either q1 or q2, which can easily switch over in a domain as
a whole. This approach explains the presence of the q2 modulation in the STM
images recorded above the T2 CDW transition and the absence of the q2
satellites in the corresponding diffraction patterns. The long periodic
modulation, detected by LT STM is attributed to a beating between the two CDWs,
centered on adjacent columns of the same type. These pairs of columns, both
either of type-III or type-I, modulated by the two alternative CDWs, represent
the basic modulation units, ordered into nano-domains
Nb S3: A unique quasi-one-dimensional conductor with three charge density wave transitions
© 2017 American Physical Society.We review the features of the charge density wave (CDW) conductor NbS3 (phase II) and include several additional results from transport, compositional, and structural studies. Particularly, we highlight three central results: (1) In addition to the previously reported CDW transitions at TP1=360K and TP2=150K, a third CDW transition occurs at a much higher temperature TP0≈620-650K; evidence for the nonlinear conductivity of this CDW is presented. (2) We show that the CDW associated with the TP2 transition arises from S vacancies acting as donors. Such a CDW transition has not been observed before. (3) We demonstrate the exceptional coherence of the TP1 CDW at room temperature. The effects of uniaxial strain on the CDW transition temperature and transport are reported
Description and applications of a 3D mathematical model for horizontal anode baking furnaces
In aluminum industry, carbon anodes are consumed continuously during alumina reduction in the electrolysis cells. Anodes are made of calcined coke, butt, and recycled anode particles and pitch as the binder. Green anodes are baked in large furnaces where they attain specific properties in terms of density, mechanical strength, and electrical conductivity. Baking is an important and costly step in carbon anode production. The proper operation of the furnace provides the required anode quality. Mathematical modeling allows the prediction of the heating profile of anodes during baking. Taking into account all the relevant phenomena, a 3D transient mathematical model was developed to simulate the different stages of the baking process in the furnace. The predictions give a detailed view of the furnace operation and performance. In this article, the 3D model is described, and the results on the impact of various parameters on furnace behavior are presented
Cold atoms in space: community workshop summary and proposed road-map
We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies.publishedVersio
Cold atoms in space: community workshop summary and proposed road-map
We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies