Observation of Bose-Einstein Condensation of Molecules (original) (raw)
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Bose-Einstein Condensation of Molecules
Science, 2003
We report on the Bose-Einstein condensation of more than 10 5 Li 2 molecules in an optical trap starting from a spin mixture of fermionic lithium atoms. During forced evaporative cooling, the molecules are formed by three-body recombination near a Feshbach resonance and finally condense in a long-lived thermal equilibrium state. We measured the characteristic frequency of a collective excitation mode and demonstrated the magnetic field–dependent mean field by controlled condensate spilling.
The history of the Bose-Einstein condensate (BEC) is considered from Einstein's original conception, to London's revival with respect to superfluid 4He and to an explanation of today's concept of the BEC as a result of broken gauge symmetry and phase coherence. A discussion of the BEC's role in superfluidity shows that BEC is neither a necessary nor sufficient condition for superfluidity. The protocol to make BEC in dilute gases is outlined from the 1995 experiment by Cornell and Wieman.
Journal of Statistical Physics, 2000
The study of low density, ultracold atomic Fermi gases is a promising avenue to understand fermion superfluidity from first principles. One technique currently used to bring Fermi gases in the degenerate regime is sympathetic cooling through a reservoir made of an ultracold Bose gas. We discuss a proposal for trapping and cooling of two-species Fermi-Bose mixtures into optical dipole traps made from combinations of laser beams having two different wavelengths. In these bichromatic traps it is possible, by a proper choice of the relative laser powers, to selectively trap the two species in such a way that fermions experience a stronger confinement than bosons. As a consequence, a deep Fermi degeneracy can be reached having at the same time a softer degenerate regime for the Bose gas. This leads to an increase in the sympathetic cooling efficiency and allows for higher precision thermometry of the Fermi-Bose mixture.
Bose-Einstein condensation: what, how and beyond
arXiv (Cornell University), 2022
The piling up of a macroscopic fraction of noninteracting bosons in the lowest energy state of a system at very low temperatures is known as Bose-Einstein condensation. It took nearly 70 years to observe the condensate after their theoretical prediction. A brief history of the relevant developments, essentials of the basic theory, physics of the steps involved in producing the condensate in a gas of alkali atoms together with the pertinent theory, and some important features of the research work carried out in the last about 25 years have been dealt with. An effort has been made to present the material in a manner that it can be easily followed by undergraduate students as well as non-specialists and may even be used for classroom teaching.
Bose-Einstein condensation and superfluidity in trapped atomic gases
Comptes Rendus de l'Académie des Sciences-Series …, 2001
Bose–Einstein condensates confined in traps exhibit unique features which have been the object of extensive experimental and theoretical studies in the last few years. In this paper I will discuss some issues concerning the behaviour of the order parameter and the dynamic and ...
Condensation of Pairs of Fermionic Atoms near a Feshbach Resonance
Physical Review Letters, 2004
We have observed Bose-Einstein condensation of pairs of fermionic atoms in an ultracold 6 Li gas at magnetic fields above a Feshbach resonance, where no stable 6 Li2 molecules would exist in vacuum. We accurately determined the position of the resonance to be 822±3 G. Molecular Bose-Einstein condensates were detected after a fast magnetic field ramp, which transferred pairs of atoms at close distances into bound molecules. Condensate fractions as high as 80% were obtained. The large condensate fractions are interpreted in terms of pre-existing molecules which are quasi-stable even above the two-body Feshbach resonance due to the presence of the degenerate Fermi gas.
Bose-Einstein condensation of lithium
Applied Physics B: Lasers and Optics, 1997
Bose-Einstein condensation of 7Li has been studied in a magnetically trapped gas. Because ofthe effectively attractive interactions between 7Li atoms, many-body quantum theory predicts that the occupation number of the condensate is limited to about 1400 atoms. We observe the condensate number to be limited to a maximum value between 650 and 1300 atoms. The measurements were made using a versatile phase-contrast imaging technique. We discuss our measurements, the current theoretical understanding of BEG in a gas with attractive interactions, and future experiments we hope to perform.
Bose-Einstein condensation in dilute atomic gases
Naturwissenschaften, 2002
Bose-Einstein condensation is one of the most curious and fascinating phenomena in physics. It lies at the heart of such intriguing processes as superfluidity and superconductivity. However, in most cases, only a small part of the sample is Bose-condensed and strong interactions are present. A weakly interacting, pure Bose-Einstein condensate (BEC) has therefore been called the "holy grail of atomic physics". In 1995 this grail was found by producing almost pure BECs in dilute atomic gases. We review the experimental development that led to the realization of BEC in these systems and explain how BECs are now routinely produced in about 25 laboratories worldwide. The tremendous experimental progress of the past few years is outlined and a number of recent experiments show the current status of the field. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.
BOSE-EINSTEIN CONDENSATION: TWENTY YEARS AFTER
The aim of this introductory article is twofold. First, we aim to offer a general introduction to the theme of Bose-Einstein condensates, and briefly discuss the evolution of a number of relevant research directions during the last two decades. Second, we introduce and present the articles that appear in this Special Volume of Romanian Reports in Physics celebrating the conclusion of the second decade since the experimental creation of Bose-Einstein condensation in ultracold gases of alkali-metal atoms.