Ultracold atomic gases

Concurrently, the world of ultracold systems has expanded its boundaries during the last decade to encompass ultracold, three-dimensional, large hnite systems [e.g., ( He)jy clusters (N = 2-10" ), and ( He)jy clusters (N = 25-10 )] in the temperature range of T = 0.1-2.2 K [6-11, 50-78], finite optical molasses in laser irradiated ultracold atomic gases in the temperature range of 10-100 pK [79], as well as finite Bose-Einstein condensates in the temperature range of 10-100 nK [14, 80],... 

Most theoretical treatments of decay consider the time evolution of an initial state tunneling out of single well [81-85]. However, the present-day possibility of designing the potential parameters of artificial quantum systems [61, 86], opens the way to study the issue of decay in more complex potential profiles as exemplified by semiconductor multibarrier systems of finite length which are formed by a succession of alternating barriers and wells [57] and other artificial multibarrier structures as ultracold atomic gases in optical lattices [86]. 

Our results are of a general validity in quantum mechanics and hence one may consider other artificial multibarrier structures as, for example, ultracold atomic gases in optical lattices [86] and in optical tests of quantum mechanics [96]. 

M. Lewenstein, A. Sanpera, V. Ahufinger, D. Bogdan, A. Sen, U. Sen, Ultracold atomic gases in optical lattices mimicking condensed matter physics and beyond, Adv. Phys. 56, (2007) 243. 

Hutson, J.M. and Soldin, R, Molecular collisions in ultracold atomic gases, Int. Rev. Phys. Chem., 26, 1, 2007. 

The coldest molecules available for experiments are diatomic molecules produced by association techniques in ultracold atomic gases. The basic idea is to bind atoms together when they collide at extremely low kinetic energies. If any release of internal energy is avoided in this process, the molecular gas just inherits the ultralow... 

The name Feshbach molecule emphasizes the production method, as it commonly refers to diatomic molecules made in ultracold atomic gases via Feshbach resonances. 

Hau LV, Harris SE, Dutton Z et al. Light speed reduction to 17 meters per second in an ultracold atomic gas. Nature (London) 1999 Feb 18 397 594-598. 

An ultracold dilute gas of bosonic atoms constitutes a many-body system of weakly interacting constituents. An attempt to bridge between the thermodynamic picture of a rounded-off Bose-Einstein phase transition and molecular... 

M. Greiner, O. Mandel, T. EssUnger, T.W Hansch, I. Bloch, Quantum phase transition from a superfluid to a Mott insulator in a gas of ultracold atoms. Nature 415(6867), 39-44 (2(X)2). doi 10.1038/415039a... 

These results provide important implications for the experiments on the production of Li Li in an ultracold mixture of Li and Li atoms. CvitaS and colleagues proposed removing quickly the Li atomic gas after the formation of the Li Li molecules... 

Staanum, R, Kraft, S.D., Lange, J., Wester, R., and WeidemuUer, M., Experimental investigation of ultracold atom-molecule collisions, Phys. Rev. Lett., 96,023201,2006. Zahzam, N., Vogt, T., Mudrich, M., Comparat, D., and RUlet, R, Atom-molecule collisions in an optically trapped gas, Phys. Rev. Lett., 96, 023202, 2006. 

The Efimov trimers influence the three-body scattering properties. When an Efimov state intersects the continuum threshold for a < 0 three-body recombination loss is enhanced [79,80], as the resonant coupling of three atoms to an Efimov state opens up fast decay channels into deeply bound dimer states plus a free atom. Such an Efimov resonance has been observed in an ultracold, thermal gas of Cs atoms [77]. For fl > 0 a similar phenomenon is predicted, namely an atom-dimer scattering resonance at the location at which an Efimov state intersects the atom-dimer threshold [81,82]. Resonance enhancement of P has been observed in a mixture of Cs atoms and Cs2 halo dimers [78] see Figure 9.15. The asymmetric shape of the resonance can be explained by the background scattering behavior, which here is a linear increase as a function of a. 

Koelman JMVA, Stoof HTC, Verhaar BJ, Walraven JTM. (1988) Lifetime of magnetically trapped ultracold atomic deuterium gas. Phys. Rev. B 38 9319-9322. 

Quantum Phase Transition from a Superfluid to a Mott Insulator in a Gas of Ultracold Atoms. 

Fig. 8.2 A quantum degenerate gas of ultracold atoms reaches degeneracy when the matter waves of neighboring atoms overlap (a) at absolute zero, gaseous bosonic atoms all end up in the lowest energy state (b) fermions, in contrast, fill the states with one atom per state, and the energy of the highest filled state at T = 0 is the Fermi energy Ep ...

A Fermi-degenerate gas can coexist with a Bose-Einstein condensate. This was observed, for example, in experiments with an ultracold atomic mixture of Li atoms (bosons) and Li atoms (fermions) at a temperature of T = 0.28/l(K and Tf=0.2Tc, where Tp and Tc are the Fermi and the Bose-Einstein condensation critical temperature, respectively (Schreck et al. 2001). 

T. Kraemer, M. Mark, P. Waldburger, J.G. Danzl, C. Chin, B. Engeser, et al., Evidence for Efimov quantum states in an ultracold gas of caesium atoms, Nature 440 (2006) 315. 

For an organic crystalline monolayer it was found that the exciton-exciton kinematic interaction can be described as scattering, not by hard spheres as in 3D crystals, but as scattering by hard disks. It was shown also that, as in the case of a two-dimensional ultracold trapped atom boson gas, the excitons in a confined monolayer may behave as a dilute degenerate boson gas at low temperature. Then for a microcavity with an organic crystalline monolayer such as a resonant material the polariton-polariton kinematic interaction steming from the polariton excitonic part was derived. 

The breakthrough experiment was carried out by Whitham et al. [39,40] in France. They used a Smalley-type laser vaporization source (Fig. 4) to provide a molecular beam of Ca atoms entrained in He or Ar gas. The second harmonic (532 nm) from a pulsed Nd YAG laser was focused (Fig. 4) on a rotating calcium rod. About 500 jus prior to this, a pulsed valve (left side of Fig. 4) is opened and the plume of vaporized metal is entrained in Ar or He gas. The carrier gas is seeded with a few percent of the oxidant such as H20. The plume of excited- and ground-state metal atoms are carried down a short channel and react with the oxidant. At the end of the channel, the product molecules such as CaOH expand into the vacuum chamber and cool. After a short expansion, the pressure has dropped so low that the molecules are effectively in a collisionless, ultracold (<10K) environment. 

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