964 research outputs found
Stable p-wave resonant two-dimensional Fermi-Bose dimers
We consider two-dimensional weakly-bound heterospecies molecules formed in a
Fermi-Bose mixture with attractive Fermi-Bose and repulsive Bose-Bose
interactions. Bosonic exchanges lead to an intermolecular attraction, which can
be controlled and tuned to a p-wave resonance. Such attractive fermionic
molecules can be realized in quasi-two-dimensional ultracold isotopic or
heteronuclear mixtures. We show that they are stable with respect to the
recombination to deeply-bound molecular states and with respect to the
formation of higher-order clusters (trimers, tetramers, etc.
Dimensional crossover for the beyond-mean-field correction in Bose gases
We present a detailed beyond-mean-field analysis of a weakly interacting Bose
gas in the crossover from three to low dimensions. We find an analytical
solution for the energy and provide a clear qualitative picture of the
crossover in the case of a box potential with periodic boundary conditions. We
show that the leading contribution of the confinement-induced resonance is of
beyond-mean-field order and calculate the leading corrections in the three- and
low-dimensional limits. We also characterize the crossover for harmonic
potentials in a model system with particularly chosen short- and long-range
interactions and show the limitations of the local-density approximation. Our
analysis is applicable to Bose-Bose mixtures and gives a starting point for
developing the beyond-mean-field theory in inhomogeneous systems with
long-range interactions such as dipolar particles or Rydberg-dressed atoms.Comment: 5 pages and supplemental material, revised treatment of the harmonic
confinemen
Observation of a Strong Atom-Dimer Attraction in a Mass-Imbalanced Fermi-Fermi Mixture
We investigate a mixture of ultracold fermionic K atoms and weakly
bound LiK dimers on the repulsive side of a heteronuclear atomic
Feshbach resonance. By radio-frequency spectroscopy we demonstrate that the
normally repulsive atom-dimer interaction is turned into a strong attraction.
The phenomenon can be understood as a three-body effect in which two heavy
K fermions exchange the light Li atom, leading to attraction in
odd partial-wave channels (mainly p-wave). Our observations show that mass
imbalance in a fermionic system can profoundly change the character of
interactions as compared to the well-established mass-balanced case
Anisotropic expansion of a thermal dipolar Bose gas
We report on the anisotropic expansion of ultracold bosonic dysprosium gases
at temperatures above quantum degeneracy and develop a quantitative theory to
describe this behavior. The theory expresses the post-expansion aspect ratio in
terms of temperature and microscopic collisional properties by incorporating
Hartree-Fock mean-field interactions, hydrodynamic effects, and
Bose-enhancement factors. Our results extend the utility of expansion imaging
by providing accurate thermometry for dipolar thermal Bose gases, reducing
error in expansion thermometry from tens of percent to only a few percent.
Furthermore, we present a simple method to determine scattering lengths in
dipolar gases, including near a Feshbach resonance, through observation of
thermal gas expansion.Comment: main text and supplement, 11 pages total, 4 figure
Synthesis, molecular structures and EPR spectra of the paramagnetic cuboidal clusters with Mo3S4Ga cores
Electron precise [Mo3(l3-S)(l-S)3(diphos)3Br3]Br (diphos = dppe,
dmpe) incomplete cuboidal clusters with six cluster skeletal electrons
(CSE) were converted into paramagnetic cuboidal [Mo3(GaBr)(l3-S)4-
(diphos)3Br3] clusters by treatment with elemental Ga. The new
heterobimetallic complexes with nine CSE possess a doublet ground
state with the unpaired electron density delocalized over the three
molybdenum atoms
Noise diodes as a source of entropy for hardware random number generators
The purpose of this article is to describe the use of digital noise generators based on semiconductor noise diodes as part of systems for generating key numerical sequences used in cryptographic security methods. The classification of modern methods of cryptographic protection and the algorithms underlying them are considered. It is shown that ensuring high information entropy in systems for generating encryption keys is possible by using generators of truly random number sequences and cryptographically secure generators of pseudo-random number sequences. A number of disadvantages inherent in widely used sources of physical noise are described, namely: low spectral density of broadband noise, limited frequency range, nonlinearity of the noise spectrum, difficulties in technical implementation when using some methods, especially under conditions of extreme temperatures and exposure to special factors. It has been confirmed that the noise properties of semiconductor noise diodes depend on the composition and constancy of the defect-impurity structure, and defect engineering makes it possible to control their electrical parameters. The study of inhomogeneities and defects in noise diodes and the development on this basis of methods for controlling the level of structural defects made it possible to create technologies for their generation and annealing, and to improve a number of electrical and statistical properties of noise diodes
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