Universality of the three-body parameter for Efimov states in ultracold cesium

We report on the observation of triatomic Efimov resonances in an ultracold gas of cesium atoms. Exploiting the wide tunability of interactions resulting from three broad Feshbach resonances in the same spin channel, we measure magnetic-field dependent three-body recombination loss. The positions of the loss resonances yield corresponding values for the three-body parameter, which in universal few-body physics is required to describe three-body phenomena and, in particular, to fix the spectrum of Efimov states. Our observations show a robust universal behavior with a three-body parameter that stays essentially constant.     

Efimov effect in nuclear three-body resonance decays

We investigate the effects of the nearly fulfilled Efimov conditions on the properties of three-body resonances. Using the hyper-spheric adiabatic expansion method we compute energy distributions of fragments in a three-body decay of a nuclear resonance. As a realistic example we investigate the 1- state in the halo nucleus 11Li within a three-body model 9Li + n +n model. Characteristic features appear as sharp peaks in the energy distributions. Their origin, as in the Efimov effect, is in the large two-body s-wave scattering lengths between the pairs of fragments.     

A model search for Efimov states

A search for Efimov states is carried out in terms of a one-dimensional model three-body problem. A numerically exact solution is obtained that allows scanning through the resonance condition. No evidence is found for the existence of an infinite number of such bound three-body states. It is deduced from one-dimensional results that such an infinity of bound states should also not arise in a complete three-dimensional calculation.     

Bose-Einstein condensates and Efimov states in trapped many-boson systems

We investigate trapped cold Bose gases using the stochastic variational approach with realistic attractive finite-range two-body interactions. We study the properties of the Bose-Einstein condensates, particularly in the large scattering-length regime, and establish the existence of meta-stable many-body Efimov states.     

Efimov states and their Fano resonances in a neutron-rich nucleus

Asymmetric resonances in elastic n+19C scattering are attributed to Efimov states of such neutron-rich nuclei, that is, three-body bound states of the n+n+18C system when none of the pairs is bound or some of them are only weakly bound. By fitting to the general resonance shape described by Fano, we extract the resonance position, width, and the "Fano profile index." While Efimov states have been discussed extensively in many areas of physics, there is only one very recent experimental observation in trimers of cesium atoms. The conjunction that we present of the Efimov and Fano phenomena may lead to experimental realization in nuclei.     

Trajectory of virtual, bound and resonant Efimov states

The pole trajectory of Efimov states for a three-body ααβ system with αα unbound and αβ bound is calculated using a zero-range Dirac-δ potential. It is shown that a three-body bound state turns into a virtual one by increasing the αβ binding energy. This result is consistent with previous results for three equal mass particles. The present approach considers the n-n-¹⁸C halo nucleus. However, the results have good perspective to be tested and applied in ultracold atomic systems, where one can realize such three-body configuration with tunable two-body interaction.     

Inhibiting three-body recombination in atomic Bose-Einstein condensates

We discuss the possibility of inhibiting three-body recombination in atomic Bose-Einstein condensates via the application of resonant 2pi laser pulses. These pulses result in the periodic change in the phase of the molecular state by pi, which leads to destructive interference between the decay amplitudes following successive pulses. We show that the decay rate can be reduced by several orders of magnitude under realistic conditions.     

Asymptotically adapted three-body molecular states

For the first time a formal theory for three-body rearrangement scattering processes in the molecular-state approach is formulated removing difficulties with unphysical long-range couplings.     

Efimov states in a Bose-Einstein condensate near a Feshbach resonance

Recent experiments with Bose-Einstein condensates of 85Rb atoms near a Feshbach resonance have produced evidence for a condensate of diatomic molecules coexisting with the atom condensate. It should also be possible to create condensates of the triatomic molecules predicted by Efimov coexisting with the atom and dimer condensates. The smoking gun for the trimer condensate would be oscillatory dependence of observables on the binding energy of the trimer. It may also be possible to deduce the existence of the trimer condensate from the spectra of the bursts of atoms and dimers created in the disappearance of the trimers.     

Microscopic three-body force for asymmetric nuclear matter

Brueckner calculations including a microscopic three-body force have been extended to isospin-asymmetric nuclear matter. The effects of the three-body force on the equation of state and on the single-particle properties of nuclear matter are discussed with a view to possible applications in nuclear physics and astrophysics. It is shown that, even in the presence of the three-body force, the empirical parabolic law of the energy per nucleon vs. isospin asymmetry β = (N - Z)/A is fulfilled in the whole asymmetry range 0≤β≤1 up to high densities. The three-body force provides a strong enhancement of the symmetry energy which increases with density in good agreement with the predictions of relativistic approaches. The Lane's assumption that proton and neutron mean fields linearly vary vs. the isospin parameter is violated at high density due to the three-body force, while the momentum dependence of the mean fields turns out to be only weakly affected. Consequently, a linear isospin split of the neutron and proton effective masses is found for both cases with and without the three-body force. The isospin effects on multifragmentation events and collective flows in heavy-ion collisions are briefly discussed along with the conditions for direct URCA processes to occur in the neutron star cooling. Received: 18 February 2002 / Accepted: 16 May 2002     

Pauli blocking effect on Efimov states near a Feshbach resonance

In this Letter we study the effect of Pauli blocking on Efimov states in a quantum Fermi gas and illustrate that the universal Efimov potential is altered at large distances. We obtain the universal spectrum flow of Efimov trimers when the Fermi density is varied and further consider the effect of scattering of trimers by the Fermi sea. We argue that the universal flow is robust against fluctuating particle-hole pairs that result in an infrared catastrophe in impurity problems.     

Micromaser action in atomic clusters

Optical micromaser action is considered in atomic clusters that can be involved in separable and entangled initial correlations. An equation describing the evolution of the Glauber quasi-probability for a light field is constructed in the Fokker-Planck approximation. The statistics of radiation emitted by a cavity is analyzed.     

Quasicrystals and atomic clusters

Historically, two principal approaches exist to determine the quasicrystal atomic structures: one is derived directly from diffraction experiments, using cut and projection of higher dimensional space-representation techniques; the other one takes use of the similarity between so-called approximant crystalline phases, observed to co-exist with quasicrystals. The known structure of these phases is shown to be the starting point of building a quasicrystal model in terms of constitutive polyatomic clusters of icosahedral symmetry. It requires to apply inflation properties of quasiperiodicity, and decoration of elementary building tiles. One example is detailed and discussed, in terms of a two-cluster model, in the case of AlLiCu.     

Electron states in metal clusters

Radiative transitions in metal clusters are analyzed in terms of quantum transitions of valence electrons that interact with surrounding valence electrons and ion cores. The analysis is based on the solution of the Thomas-Fermi equation for valence electrons in a spherical cluster. The quantum states of valence electrons and the energy and the dipole moments of transitions are determined in the quasiclassical approximation. It is shown that the frequencies of dipole oscillations and the dipole moments of the transitions strongly depend on the size of a cluster.     

Bond orientational order in atomic clusters

Bond orientational order parameters for the global minimum energy configurations of a number of Lennard-Jones and Morse clusters are calculated. The results demonstrate that the bond orientational order parameters, particularly the third-order invariants, provide a fairly discriminating set of symmetry markers for different cluster geometries. Since they are relatively easy to calculate from simulation data, they may be useful in studies of local order in a wide variety of contexts, including studies of melting, nucleation and the glass transition     

Giant light enhancement in atomic clusters

We show that the polarizing effect of the atoms in an atomic cluster can lead to full compensation of the radiative damping of excited atomic states, a change in the sign of the dispersion of the atomic polarizability, and giant light enhancement by the atomic cluster.     

Effect of three-body interaction on hot asymmetric nuclear matter

The properties of hot asymmetric nuclear matter are studied in the framework of the finite temperature Brueckner－Hartree－Fock theory that is extended to include the contribution of microscopic three-body forces. We give the variation of the critical temperature with the asymmetry parameter and show the effect brought by this three-body repulsive potential on the value of the critical asymmetry of the phase transition for asymmetric nuclear matter. Owing to the additional repulsion provided by three-body forces, this value decreases. In addition, the domain of mechanical instability for hot nuclear matter is also indicated, which gradually shrinks with increasing asymmetry and temperature.