The 4He Trimer as an Efimov System

Kolganova, E. A.; Мотовилов, А. К.; Sandhas, W.

doi:10.1007/s00601-011-0233-x

Cited by 45 publications

(44 citation statements)

References 95 publications

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“…The excited state has one node in the hyperradial coordinate, indicating a vibrational excitation that is reminiscent of a breathing mode in classical tri-atomic molecules. Our calculations, shown by the green and red lines in Figure 1A, conclude -in agreement with earlier works (4,10,(13)(14)(15)(16) -that an artificial strengthening of the pair interaction (see the right pointing arrow above Figure 1A) renders the excited state of the helium trimer less strongly bound with respect to the dimer, thus confirming the Efimov character of the trimer state. This character is further supported by the appearance of a 3 second Efimov state upon an artificial weakening of the true two-body He-He potential (dashed black line labeled "2nd ES" in Figure 1A).…”

Section: One Sentence Summarysupporting

confidence: 91%

Observation of the Efimov state of the helium trimer

Kunitski

Zeller

Voigtsberger

et al. 2015

Science

220

219

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Quantum theory dictates that upon weakening the two-body interaction in a three-body system, an infinite number of three-body bound states of a huge spatial extent emerge just before these three-body states become unbound. Three helium atoms have been predicted to form a molecular system that manifests this peculiarity under natural conditions without artificial tuning of the attraction between particles by an external field. Here we report experimental observation of this long predicted but experimentally elusive Efimov state of 4 He3 by means of Coulomb explosion imaging. We show spatial images of an Efimov state, confirming the predicted size and a typical structure where two atoms are close to each other while the third is far away. One Sentence Summary:We report experimental discovery of a gigantic molecule that consists of three helium atoms and is bound solely by a universal feature of quantum mechanics called "Efimov effect".Ever since the early days of celestial mechanics, the three-body problem posed a major challenge to physicists. In the early 20th century the failure of finding a stable solution for the classical helium atom (2 electrons and a nucleus) heralded the demise of Niels Bohr's program of semiclassical atomic physics (1). Quantum mechanics then added yet another surprising twist to the three-body problem when in 1970 Vitaly Efimov predicted the appearance of an infinite series of stable three-body states of enormous spatial extents (2). These Efimov states are predicted to exist for short-range interactions like the van der Waals force between atoms or the strong force between nucleons. When the potential becomes so shallow that the last two-body bound state is at the verge of becoming unbound or is unbound, then three particles stick together to form Efimov states. Intriguingly, this three-body behavior does not depend on the details of the underlying two-body interactions. This makes the Efimov effect a universal phenomenon, with important applications in particle, nuclear (3, 4), atomic (4), condensed matter (5) and biological physics (6).Figure 1 summarizes two facets of Efimov's prediction, namely the energy spectrum and the structure of an Efimov state. Figure 1A shows how the two-and three-body binding energies (the binding energy of an atomic cluster is defined as the energy needed to separate all constituents of the cluster to infinite distances) change as the depth of the two-body potential is increased. As 2 indicated by the arrow above Figure 1A, the depth of the two-body potential increases along the horizontal axis. As the depth increases, the s-wave scattering length a changes from negative values to infinitely large values to positive values. Negative a values correspond to the domain where shallow two-body bound states do not exist. For positive a, a shallow two-body bound state, the dimer (see the blue solid line), exists. Bound three-body states (called trimers) exist in the green-shaded area. The extremely weakly-bound three-body states close to threshold (see...

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Section: One Sentence Summarysupporting

confidence: 91%

Observation of the Efimov state of the helium trimer

Kunitski

Zeller

Voigtsberger

et al. 2015

Science

220

219

View full text Add to dashboard Cite

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“…As X increases, the states that disappear are Efimov states while any states that remain are normal states [15,16,25], For the 7Li4He2 system, it is interesting to adjust Li-He interaction through X to make the relevant two-body binding energy in the range of the newly reported experiment value [27], Through the calculations, we can identify whether, within a realistic range of variation of X, states having Efimov characteristics would be found.…”

Section: Efimov Character For the Excited Statementioning

confidence: 96%

“…States w ith Borrom ean character are w ell established in nuclear physics, but Efimov states have not been found. So far the m ost prom ising m olecular system for the Efimov effect is the helium trim er w hich has been predicted to have two bound states and the excited state has Efim ov nature [15][16][17], However, the expectation has not been confirm ed by the experim ents on m olecular beam s [18,19]. Besides the well studied helium trim ers, there is also grow ing interest in the study o f van der W aals m olecules H e2 X (X = alkali-m etal atom ), w hich are w eakly bound and may also exhibit Efimov states naturally [20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Prediction of a weakly bound excited state of Efimov character in aLi7He24system

Han

et al. 2014

Phys. Rev. A

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We carry out calculations on the van der Waals trimer ' Li4He2 using the mapping method within the frame of hyperspherical coordinates, which allows us to give accurate binding energies and wave functions for both the ground and excited state of the system. When the realistic two-body potentials are adopted, the system presents an excited state which shows Efimov character. We study the range of the interaction strength in which the excited state could exist and find that the state persists within the experiment error band for binding energy of LiHe molecule. We also study the three-body parameter (3BP) of 7Li4He2 system and its relationship with the background scattering length a HeHe-Our calculations demonstrate that the 3BP of 7Li4He2 system is dependent on the value of the scattering length «HeHe> independent of the short-range details of the He-He interaction. The results confirm the prediction of Wang etal. [Phys. Rev. Lett. 109, 243201 (2012)] that the 3BPfor a heteronuclear atomic system is universally determined from the van der

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“…Indeed, according to aforesaid the atoms in quantum liquid are delocalized and thus nothing prevents them from getting involved into multiple-body interactions where the multiplicity can vary from two to the total number of atoms in the system. An example of multi-body (three and more) interactions being very important for forming bound states of bosons at low temperatures is the Efimov state [23,24] which has been experimentally observed in helium [25], a recent review can be found in [26].…”

Section: Collective Variable Theorymentioning

confidence: 99%

Volume element structure and roton-maxon-phonon excitations in superfluid helium beyond the Gross-Pitaevskii approximation

Zloshchastiev

2012

Eur. Phys. J. B

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We propose a theory which deals with the structure and interactions of volume elements in liquid helium II. The approach consists of two nested models linked via parametric space. The short-wavelength part describes the interior structure of the fluid element using a non-perturbative approach based on the logarithmic wave equation; it suggests the Gaussian-like behaviour of the element's interior density and interparticle interaction potential. The long-wavelength part is the quantum many-body theory of such elements which deals with their dynamics and interactions. Our approach leads to a unified description of the phonon, maxon and roton excitations, and has noteworthy agreement with experiment: with one essential parameter to fit we reproduce at high accuracy not only the roton minimum but also the neighboring local maximum as well as the sound velocity and structure factor.

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The 4He Trimer as an Efimov System

Abstract: We review the results obtained in the last four decades which demonstrate the Efimov nature of the 4 He three-atomic system.

Cited by 45 publications

References 95 publications

Observation of the Efimov state of the helium trimer

Observation of the Efimov state of the helium trimer

Prediction of a weakly bound excited state of Efimov character in aLi7He24system

Volume element structure and roton-maxon-phonon excitations in superfluid helium beyond the Gross-Pitaevskii approximation

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